What do you think of this tattoo idea?

If it's something that means a lot to you then go for it. Only problem i see here is when people want to get wrist tattoos, they typically want it to be small. if you want detail on the roman numeral it's going to be bigger than what you want probably. I don't really have any ideas for colors other than maybe yellow like a canary since you grandpa checked for gas. You could also get a canary on top of the roman numeral to symbolize your grandpa and have your bday.