I agree Neko. My kitten Waffles had it from 3 weeks. We treated topically until he was 8 weeks old, and then our vet put him on a week long low dose of Itraconozole. He cleared up, then I got 2 patches of it, one on my arm and one on my stomach, it was itchy, and looked like a perfectly round spot of poison ivy. I treated it with OTC creams, and it went away, my cat Kodak got a spot of it, we treated him orally with a medicine in pill form, it cleared up, one of my spots flared up, more OTC cream, and now (knock wood) everyone is clear. My boyfriend never got it, none of my other cats got it. All were healthy and had strong immune systems. I caught a cold the week I broke out with it initially, and Kodak was diagnosed with a UTI when he broke out, so both of us were immune compromised. I cleaned really well, washed bed linens more often, and washed my hands a lot after handling Waffles initially, but one can only do so much when you're trying to bottle raise a demanding mouthy grump of a kitten (hehe)
So basically, having ring worm is annoying, but it wasn't like it was painful, and since I started treatment immediately, it was gone quickly.
I read somewhere, when I was researching ringworm in cats and kittens, that the grey discoloring was common with the infection. HOWEVER, I would continue topical treatments for a while after the sore is gone, because it can flare up (after it looks better) and then it can become resistant to topical meds. I found that Lamisil cream worked best on myself, but since Waffles and Kodak were already on oral meds when I got my outbreak, I never asked if the Lamisil was safe on cats. (it has a different active ingredient than other OTC antifungal creams) But Lotrimin cream is safe for use on our fur babies.