Careful though, the colouring is not the best basis for identifying slots types.

Many PCI-Express x16 slots are black or blue, but they can also be white, yellow or orange. Nearly all x1 slots are white. For AGP, I have seen brown, orange, green, blue, purple and yellow. I'm sure there are many other colours for either slot type that I have not seen or do not recall.

The best way to identify slots is by shape. Here is one of those nasty PCI-Express and AGP supporting motherboards, but it's good for comparison



The long, narrow white slot at the top is PCI Express x16, down from that are two white PCI Express x1 slots, followed by an AGP 3.0 slot in classic brown.