Theres 4 types of video card slots right (ISA, PCI, AGP, PCIe) does anyone know the colours of these slots?

Yes. The ISA slot always stayed in Black color. AGP slot, Brown. Usually the PCI slots are White, but I have seen some boards where the PCI-Express 2.0 x16 slots were Green, and the PCI slots were Black. PCI-Express slots may vary in color. I believe if this were an answer to a test, you could p with, ISA=Black, AGP=Brown, PCI=White, and PCI-Express x16=Blue (Don't forget that PCI-Express 2.0 is out now!)