Good question. But overriding that is the question of what the condition is of any lens you're bound to get your hands on. It seems miracle enough to get a lens without "cleaning marks". Coatings on used lenses are now a distant second in finding good lenses.
The coating color is just an iridescent lighting effect of the various compounds used to coat the lens. I notice most of the Nikon lenses of latter years to favor a lot of green, for instance. But it's only because of the various methods and compounds they found in their R&D. The actual coating actually are perfectly clear--just like a soap bubble.
To my knowledge all surfaces had at least one coating, after the era of coating began. I am no expert. Just wait for someone come along and correct me. That would be fine. Till then, my answer is reasonably good for boob purposes.