I don't know of any product but you can probably disguise these as long as your prepared for a bit of a fiddle, I have just used polyfilla in the past but if the holes are at eye level you would be more aware of them. How I would probably tackle a noticeable area is still with polyfilla, obviously ensure rawlplugs are removed and any rough bits around edges of hole are smoothed.
To get the colour either paint the polyfilla after filling, while still soft (poster or acrylic paints probably best) so the colour soaks in or if you have an emulsion that is the colour wanted mix the polyfilla up with the paint only - don't add water. You could also try mixing it with humbrol or enamel paint to get it the right colour. When its dry if you want it to 'shine' more try a clear varnish. I think I would first try clear nail varnish as wood varnishes tend to be a bit yellow.
If you're fussy you may have to experiment. This would be better if you had an off cut, even of a different tile. The nail varnish may need periodic replacing depending on what you clean with. If you fill the hole directly and are very unhappy with result at least you should be able to remove with a fine drill if you have to. Easiest way is to make up your mind before its really set and then rake out with a fence nail. Good luck
Jane
January 2008