elsacoon, All I do is go the garden centre and follow my nose. They all have different kinds of fragrance and since frangrance is so personal - it's best for you to experience that for yourself. You could also contact the Royal Botanical Garden because they have the world's largest collection of lilacs. They recently had a sale but you can still visit their site.

I had one (white) that has a fragrance reminicent of jasmine. I wish I had kept the name but I hadn't. Lots of regrets there.