How do you say pink diamond Japanese?

I don't think there is a Japanese Word for "diamond". At least google Translate translates it as 'daiyamondo'. In Chinese, 'diamond' translates to 'Zuan Shi'. But if you want to say 'red jewel', perhaps "akai houseki" (or possibly "akai no houseki" -- though I would go with the former) would work. I hope that helps!