What to do? (shy to go nude in public), and my partner has suggested to go to body painting event to bring some spice to our relationship.?

nutella is your friend and you don't have to leave home

Show up your talent, dont worry at all.

I have an idea, but some body paint and a big tarp, and paint each other naked at home.

Think of other things too, there could be lot many other ways to spice things up between a couple. If a partner feels uncomfortable the act shouldn't be insisted to be performed. Convey your comfort level.

So you say 'no, I'm not comfortable doing that'.

Spicing things up only works if both partners are having fun. For you this isn't fun. So it's the wrong kind of spice.

I don't mean you should get angry. It's good that your partner comes up with suggestions like this. It's just that this particular one won't work for you personally. Maybe you can suggest an alternative.

Where is your sense of adventure?

Don't do anything you're uncomfortable doing. Lots of other females wouldn't want to do that either. Stand your ground and say you're not interested. It's your prerogative to say no.