Christian:
I thought I'd take a few minutes to explain where paints get their colour from, and why some kinds of colours fade less than others. Most of what I'm going to be talking about are something called "inorganic pigments", which are much less vibrant in colour than organic pigments. So, inorganic won't give you the colour shock that some organic pigments will. However, knowing the advantages and disadvantages of inorganic pigments will help you make a decision on which colour to go with.
Paints, unlike stains, get their colour from "Pigments". Pigments are solid coloured particles suspended in the dry paint film very much like the raisins in raisin bread. Wood stains are really nothing more than brown dyes dissolved in either mineral spirits or alcohol, but both latex and oil based paints are a "SLURRY", which is solid particles suspended in a liquid. Both oil based and latex paints get their colour (and some to most of their opacity) from the coloured pigments in the paint. Most of the time those pigments are added to the paint in the form of a liquid colourant dispensed by the paint tinting machine at the place where the paint is sold, but you can still buy some factory pretinted paints, although they're becoming much less common than they used to be.
Pigments fall into two catagories: organic pigments and inorganic pigments.
Actually, that's a blatant lie; there are both synthetic and natural organic pigments and synthetic and natural inorganic pigments, for a total of 4 catagories, but let's ignore all the natural pigments since the pigments in house paints are all synthetic. BUT, keep in mind that the synthetic inorganic pigments used in house paints have properties identical to the natural inorganic pigments that artists have been using for hundreds of thousands of years. (Stone tools which appear to have been used to grind up coloured rocks have been found in Africa and dated to over 350,000 BC, and cave paintings of the same colour were found in that area.)
Organic pigments are made in laboratories out of chemicals, (usually with the aid of a hunchback and a bolt of lightning). Organic pigments are all the colourwheel colours; like red, blue and yellow (Napthol Red, Phthalocyanine Blue and Diarylide Yellow, respectively). They're called "organic" pigments because their chemistry invariably includes carbon atoms. Green, magenta, orange, and other bright colours can be made by mixing red, blue and yellow pigments, but there are in fact inorganic pigments that are Phthalocyanine Green, Quinicridone Magenta and Benzimidazilone Orange in colour, and these are used to make the Hunter green, magenta and orange colourants in paint tinting machines. Almost every paint company uses Phthalocyanine Blue and Phthalocyanine Green for the Navy Blue and Hunter Green pigments, respectively, cuz they're cheap and have reasonably good hide and colourfastness. Organic pigments look like little pieces of coloured plastic under a microscope. Depending on the pigment, they can look like clear plastic, transluscent plastic or opaque plastic.
Inorganic pigments are a whole nuther kettle of fish. These are the modern day synthetic equivalents of the pulverized coloured rocks that artists have been using for millenia, (hundreds of millenia, actually). Ever since the first cave men used carbon from a fire to draw a mammoth on a cave wall, artists have used natural inorganic pigments (most of which are coloured rocks pulverized into a fine powder) for artistic purposes. As far back as 2000 BC, the ancient Egyptians used different metallic ores (from which they made lead, copper and gold) to make coloured glass and ground up that coloured glass to make coloured glass dust (called "frit") which they used as a pigment to decorate Plaster of Paris (which is referred to in the Bible as "Alabaster"). Leonardo and Michaelangelo used finely pulverized rock dust like Sienna, Ochre and Umber mixed with walnut oil or poppyseed oil to paint the Sistine Chapel and the Mona Lisa. (Sienna is a yellowish rock found near the Italian town of Siena after which it's named, and when you pulverize that rock into a fine powder and mix that powder with a drying oil (like linseed oil, Tung oil, walnut oil or poppy seed oil), you effectively are making yellow oil based paint.
http://en.wikipedia.org/wiki/Pigment
Now, not all pigments are equal.
The organic pigments (red, blue, yellow) used in house paints all have relatively poor hide compared to inorganic pigments. Also organic pigments all are much less chemically stable than inorganic pigments, so they fade more from exposure to Sunlight. (So, for example, yellow cars do not use an organic yellow pigment like house paints do cuz they'd fade to the colour of the primer underneath in a decade or so.) The yellow pigment used to make yellow automotive paints years ago (before they used clear coats over the paint on cars) was bismuth vanadate, which is a bright yellow INORGANIC pigment; a pulverized rock. Bismuth vanadate is a bright yellow pigment similar in colour to Canary Yellow. Special high performance pigments are expensive, so automotive paints cost several hundred dollars per quart, compared to $35 per gallon for a decent quality house paint.
Now, a little bit of common sense (that'll be easy to understand and remember):
Every kid knows that rocks are opaque. You can hide from other kids if you hide behind a big enough rock. So, if you pulverize a rock into a fine powder, the powder you get is the same colour and opacity as the rock was. Thus, pulverizing coloured rocks into coloured dust and mixing that dust into a drying oil to make paint results in paints with very good hide. That's cuz the pigment particles from which the paint gets its colours are quite opaque.
Also, rock are extremely good at being old. There are few things you come across in daily life that are as old as the rocks in your garden. The exception would be the diamonds in your jewelry that are believed to have formed about 2 to 3 Billion (with a B) years ago, when all life on this planet consisted of single celled organisms floating in the primordial oceans.
In order for anything to even be 300 million years old (like rocks are), it has to be extremely chemically stable or it would have decomposed by now. The extreme chemical stability of rocks means that if you pulverize them into a fine powder and use that powder to colour paint, the chemical stability of the rock manifests itself as excellent resistance to fading from exposure to UV light from the Sun. This is an important consideration in a well naturally lit room (or in exterior paints) if you're ever wanting to repair and paint over nail holes in your paint (or repaint a window sill and hope the sill matches the rest of the window frame). Whenever you want the new paint to be the same colour as the old paint, that's best accomplished with a paint that uses any combination of inorganic pigments for it's colour. (Proof in Point: The Apollo IX astronauts collected rocks from the Moon that had been exposed to direct and intense sunlight for literally millions (prolly Billions) of years. But, there is no distinguishable "fading" in the colour on one side of any of those rocks. Such is the chemical stability of rocks. Over literally millions of years, there is no perceptible fading from exposure to intense UV light from the Sun, and that's even more-so on Earth which has a protective atmosphere. You can use that extreme chemical stability to make a more informed decision when choosing a colour for a paint that you don't want to fade.)
Alternatively, by knowing a little about pigments, you can be aware of some of the problems you might face in painting that depend almost entirely on the colour you choose.
This post is longer than 10,000 characters, so I have to break it up into 2 posts: