The natural lens delay some part of near ultraviolet spectrum. As a result, a large number of people with an artificial lens after cataract surgery can see ultraviolet light. Usually as shades of purple.

There is some suggestion that Claude Monet could see it.

http://www.skepticalartist.com/2013/06/25/claude-monet-and-ultraviolet-light-did-the-master-impressionist-painter-have-uv-supervision/

Thank you very much, nevertheless I still have no idea about the "appearance" of colors, or can we, as humans, imagine the "temperature" of colors that we cannot see ?

The trichromatic color vision theory suggests that human is not able to feel colors outside of this model (exept potential tetrachromats women http://nexthumanproject.com/references/Tetrachromats.pdf). Any color corresponds to exact excitation pattern of three types of cones. Even if one can see some extra light, he can realize it only with his own cones. Some exitation pattern will arise, and person will see color corresponding to this pattern (exist in trichromatic space).

The color temperature of a particular color is apparently a purely psychological phenomenon. For example, the hottest stars have a blue hue, while in our culture this color is otherwise considered cold.

What is your definition of appearance? It is our neurological manifestation that generates an appearance. Even in the visible range, many people see different colours differently depeding on their development, experience, neurophysiology and/or disease condition.

Though it seems to be an interesting question, but the terms first need to be defined.

Yes, thank you, that's exactly what I want to know. It is true I always asked myself the question of knowing that other people perceive the colors in the same way as me or, for example, what I see in green for them is red or blue? Not only Daltonism ! But also, what is there beyond the purple or below the red?