Please shoot me down if I am way off base here but if Blind people are asking you to include colour in your alt text then it's not OK for sighted people to refuse because they "feel" it's not relevant for people who were born Blind.
1) Not every Blind person is born Blind.
2) Plenty of people who aren't Blind use alt-text for various reasons.
3) What Blind people are saying is more important than what a sighted person "feels" is true.