So let’s say this Alien eyes see on the infrared level, he would see normal RGB like you and I, but could be still know there is colors there? What reason is there for the alien to discover there is colors there?
I think I can’t imagine how we discover something that we don’t see, or mostly that there is something that I don’t know
Read the book Hail Mary by Andy Weir. He explores the alieness of an alien really well and this was one of the hurdles to understanding between the two protagonists.