Brass floats will typically chance color due to what ever they are exposed to. This even takes place when exposed to water. Since our fuel is often a single product or a combination of things as well as often water (from contamination or moisture/condensation) this is "normal". Guess someone could search for all the scientific reasons and explanation on the web. Its surely there.
The collection on your float looks different from others I've seen as far as texture and build up but no telling what is in the fuel in your area or from your supplier
Bottom line, since your driving - check and or change the fuel filter since there is a good chance that some of this is floating in the fuel system and will create issues for you in the carburetor at some point.
Retitled the thread slightly and I'm moving this to a more general area so that more eyes see it since it applies to all years and models