As I understand it, healthy grape leaves turn golden color. Leaves that have fungus are red, orange and purple. However, the fungus doesn't affect the grapes unless it gets so bad that it interferes with photosynthesis. Also interesting is that many vinyards have roses at the end of each row. This is their "canary," with miners use to detect gas in the mines. In this case, roses are subject to the same diseases as grapes, but begin showing symptoms much sooner.

For my part, I prefer the ones with fungus, as they are very colorful.