Attention! You need to use with Forge the OptiFine mod for it to make it working!
This resource pack is about the rainbow sheep, which is rare, but not impossible to find of them. You have chance to find of them anywhere, where you can see sheeps. Of course you have a small chance to get of them at breeding too. I mean any sheeps too The resource pack is for 3 versions in the same time, for 1.11(.1, 2), for 1.12(.1, 2) and for 1.14(.1, 2, 3, 4). From now on with this 16 x 16 resource pack you no need anymore to give the "jeb_" name to your sheep, if you want make him/her rainbow colored. That rainbow sheep is not like who is change his/her colors, he/she have just rainbow colors, that's all. So you can't get rainbow wool, what is a bit sad, but not a big problem. So most of times you can get white wool from the rainbow sheeps too. I said "most of times", because rarely you can find them as darker rainbow sheep. The darker ones give you black, or gray, or brown wool, when you shear, or kill them. And of course that's why, if you recolor with any dye the rainbow sheep, he/she will get other rainbow color for it, like the black, gray, brown too. Good luck to explore and find at least 2-3 rainbow sheeps!
Of course you can see some screenshots about the changes in the Images.
If you doesn't know how to add to the Minecraft a resource pack, i help you in that. After you downloaded the ZIP file to your Minecraft version, don't extract it, or it won't work. Copy the ZIP file in your Minecraft folder to the resourcepacks folder. After that run the Minecraft, go to the Settings, choose the Resource Packs and there add it to the Minecraft, wait a bit, after it's done. If you did it well, it should be working.
Here is a mod for which the mod's creator added as a little extra (i asked him) the brown mooshrooms for 1.12.2, 1.11.2, 1.7.10 and other older versions too, click here to check it! In that mod the brown mooshrooms can be breed with red mooshrooms well, not like in the Brown Mooshrooms mod, where it's sadly impossible.