In a Well temperament, each of the 24 keys has a different characteristic ‘feel’ that is largely determined by the beat rates of the major/minor thirds and fifths. A very romanticised and, uhhh, colourful description of key colours was written by Christian Schubart in 1806. You can read a translation here.
In Equal temperament all keys have the same character. This renders meaningless the key choices that composers made in the Baroque, Classical and Romantic periods. And that pretty much covers the vast bulk of piano repertoire that we play and listen to the most.
Equal temperament? Just say no!