Interface of loom. Multicolor carpet.

[grandfather_pahomich 6]

 If you want to weave carpets you can put colored strings. You open interface and add strings in loom. Exit to interface and start weave. In output we have multicolor carpets. I hope that no such idea has not yet offered.

[Terex 108]

You're not explaining how to get coloured string. Right now, you can apply colour with dyes after making the wool and turn them into carpet vanilla minecraft style. Works for me.

[CorpseDrop 17]

I suppose he is suggesting to make carpets akin to minecraft banners, with more than one color per carpet and possibly different designs.

The easiest way to do this would be to use a texture pack that replaces carpet textures to more sophisticated versions.

[grandfather_pahomich 6]

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You can paint string colorant. After you should weave with other strings. As on picture from above. Carpet can also have a fringe. If you find it difficult to understand what I'm saying I want to introduce the interface: 

|View of carpet |-color strings-

  -color strings- 

The yarns and string  verticaly woven horizontally between a pattern forming.