Quite a few, but by no means all. Some are actually poisonous, so it’s important to take care when selecting your blooms. Happily, quite a number of common varieties can be eaten, among them lilacs (one of my personal favorites), pansies, petunias, daisies (English), hollyhocks, nasturtiums, roses, tulips, honeysuckles, violets, hibiscus, orange and apple blossoms.
The smaller the flower the better they hold up, since a sugar-encrusted petal of, say, an apple blossom tends to want to break away from the axis due to its weight. But then there’s nothing that says you can’t garnish your desserts with candied flower petals now is there?
Of course it isn’t necessary to add coloring to your sugar if you’d rather not. Simple white looks great on violets and roses. The only practical reason for adding color is if you intend on keeping them for a long time, since the original colors tend to fade.