Green and purple are a good color match. Of course if you want to get into the full tertiary you could add some orange to round things out but I think this is looking pretty nice. Do you care? No? Either do I. Just eat it!
I love the motif of kind of spiky flowers like this on baked goods. It contrasts nicely with the soft roundness of the cake itself, don't you think? I don't know much about flowers but I bet you guys do; are there real life spiky flowers like that out in the wild?