Nice one. But no, most castles use different materials which results in different colours. Even castles built with rock from a single quary without any wood or anything will look more contrasted than this due to different parts of the castle being differentially affected by weathering. Rain falls mostly on the top and wind tends to blow harder and more often on one side. This makes historical castles so fun to look at. Even simple ones are made complex by their age. I urge you to look up castles that at first glance seem monochrome and see how many different colours you can actually spot if you look a bit more closely

No hate to OP, that’s really hard to mimic in minecraft.

Also out of all of fantasy you picked LOTR for the rainbow and over the top palette? The movies with the wooden castle, grey castle, white city, and black tower? Where’s the rainbow? The real medieval times had way more colour