Call of Duty: Modern Warfare already offers a ton of customisation options which include dozen of weapon skins but interestingly, solid colours are not one of the available options in the game.
If you play Call of Duty: Modern Warfare regularly, you have probably unlocked a ton of customisation options for your weapons including charms, stickers and weapon skins. The first two may be a bit harder to unlock but skins are usually the easiest one and the majority of skins require simply getting kills in various ways.
Skins are split into ten categories such as digital camo, spray paint, woodland, tiger, stripes, reptile or skulls camo. Each of these categories features a number of different skins but this still is not enough for some players who would love to see an option for solid colour skins.
Just like the name suggests solid colour skins are basically simple skins that feature only one colour, you may have seen them in other games such as The Division 2. Some players like it simple and minimalistic and by the looks of it, Infinity Ward will grant their wish in the near future.
Joel Emslie, Studio Art Director at Infinity Ward replied to a Reddit post by saying that this may look like a simple thing to do but in reality, that is not the case. However, he is a big fan of the solid camos himself and the studio will look into it. "Nothing is simple in game development ;)....but! Totally agree and we are looking into it. I'm a big fan of solids myself," Emslie wrote in his reply.
Of course, this doesn't mean that solid colour camos are most definitely coming to Call of Duty: Modern Warfare but they are on the list and could be introduced in one of the future content updates such as Season 02.