Hello I noticed that some truck has two colors but I can change it that just one is this normal? and if so can you change the two colors? and how?
There are special paint designs called Two Tone and Alternate Two Tone for some vehicles. You equip it and use the 2nd color palette for the 2nd color.
I should also specify that those two tone options are found in the part selector, which is openable with ctrl+W.