Getting rid of “u” in a small subset of words is a terrible way to try to simplify English. The fact that some words in standard English (as opposed to American English) are spelled the same as the source words from French is a major benefit.

Properly simplifying English would involve getting rid of the situations where one letter can make multiple different sounds. If you’re changing it, a word like “colour” should start with a “k”, the unambiguous letter that makes that sound. A word like “cell” should start with an “s”. Really, “c” should never make either an “s” sound or a “k” sound. Maybe it could be used in place of “ch”, instead of needing two different letters to make that one sound.

If you wanted another place to start in simplifying English, you could tackle letters using “oo”. There’s no way that “oo” should make different sounds for “pool”, “flood”, “book”, “door”.