Synthesis of chlorophyll sounds like an undertaking of Woodwardian proportions. If you're interested in that general ring structure, I'd try something like porphryns or phthalocyanines. They seem pretty straightforward and are usually pretty colors to boot.
If exotic mechanisms are your thing, I'd go through a named reactions book and find one which seems interesting. If its structures you're after, I'd leaf through the Merck Index until one pops out at you.