Tetrachromats: people who see colors invisible to most of us (2014)
My spouse is a tetrachromat, and it's fascinating. Sometimes she sees patterns on leafs or bird feathers that other people don't see. Sometimes she can detect a very minor difference in colors of clothing items that other people see as identical. If a person wears those two items of clothing together she finds it really irritating.<p>She also sometimes see colors in her dreams that are outside of a pallet humans see in real life, but after she wakes up she can't describe them. It's not one color or one hue, there are several colors that she can only experience in her dreams.