If you want ot modify your carvariations.meta file heres what each line do.

cars that support interior colors and rims colors ( not all car have color-able interior/rims)
       <Item>
          <indices content="char_array">
            24 //Primary
            38 //Secondary
            35 //Pearl
            90 //Rims
            31 //Interior
            27 //?
          </indices>
          <liveries>
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
          </liveries>
        </Item>





Cars that don't ( rims are colorable on most of the cars and may cause the car to not spawn or maybe crash the game)

       <Item>
          <indices content="char_array">
            0 //Primary
            0 //Secondary
            0 //Pearl
            0 //Rims
          </indices>
          <liveries>
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
          </liveries>
        </Item>