Re: Dress code for guests??
For mehndis/mayun, it's kind of given that you should wear yellow/green/orange. Alot of people tend to stick with those colors so you don't even have to tell people about it. As for the men, generally I see them wearing shalwar kurta so at my mehndi, we gave them yellow dupattas to wear. However, I don't like it much when girls wear the SAME exact oufits, it begins to look like a uniform.
Weddings are the hardest to coordinate with your guests because living here, not everyone has a VARIETY of clothes or can just head out to get a new outfit like you can in Pakistan. Alot of people wear what's accessible to them. However, it's definitely do-able within the family and relatives. For some reason, I think it's much easier for men to coordinate with each other than women.