Why can't I pick a favourite colour?

I always have this problem of picking a favourite colour for something (car, clothes, etc.). At different times, I like different colours but I can’t pick one as my favourite. This happens with other stuff as well – picking a book, food, people… almost everything – picking one makes me unhappy. I can’t idolise (or demonise) almost anything.
Can you relate? I’d like to know why this happens.