The color scheme I decided on for my Chaos Space Marine chapter is mostly black with bone colored highlights, so those are the colors on the vehicles. Painting vehicles is interesting. It took a few coats to cover those big, flat spaces completely without having streaks. And it took a few coats to paint the bone color over the black.
There are a lot of boring flat areas, so I used some decals to make it more interesting. The icon of my chapter is a white skull, so I put some skulls on the front. I also used transfers to add numbers and some writing. The twin-linked bolter on the Predator is attached by magnet, so I can take it off and replace it with a havok launcher if needed.