So you may have noticed that sights, and possibly suppressors, come in a variety of colors and patterns but they only have the one generic thumbnail in the inventory. Only way to make sure you're not horribly mismatching color palettes on your gun is to equip a scope, exit to the main inventory to see the weapon in V's hand, go back to the weapon, swap for another sight, rinse, repeat. Either let the thumbnail show what color the sight is, or let us customize weapon and attachment colors.