You can ask for any color you need. I say things like can I please have _____, I was lucky with it last night. Or Can I have _____, It's my lucky color.
I have harvested 3 colors in one session by switching around saying brown don't seem to be lucky, let me try blue.

As for minimums, I don't mean chip value but table bet minimum. I will buy in at 10 dollar tables, but not at 15 to harvest.
Barry