Answer: Weather conditions will have a big effect on the incidence of fungal growth in mulch, as will the source of the wood used in the mulch. The fungal growths are not harmful to plants and help break down the mulch as part of the natural process of decay. So they are not bad in and of themselves although they can sometimes look alarming. Raking the mulch to fluff it and help it dry out can be useful in the short term if the weather cooperates, as will layering it no deeper than three inches thick.
As far as color, there are some colorized mulches that tend to hold their color over time, however be sure to investigate what type of wood is being used. Otherwise natural mulches do change color, it is unavoidable. To some gardeners, this is a natural progression and quite acceptable. If you do not like the look, rake or fluff the mulch from time to time and top up your mulch with a fresh layer periodically. This will help keep it looking fresh and new. Add only a little at a time however, the mulch should not be deeper than three inches.
There are many different products sold as mulch, ranging from bark to chipped branches to scrap wood such as pallets that have been shredded. You might want to consider using a different type of mulch such as shredded hardwood bark or pine bark. In my experience these are less likely to be affected by the assorted fungus and mold growths.
If you want to stay away from wood, you might try a very light layer of lawn clippings which is replenished often. (If applied in a thick layer the clippings mat together and repel water.) Also be sure they are free of herbicides.
Or, you might try using half finished compost (terrific for your plants and soil) or even use leaf mold which is basically just shredded, half rotted down, autumn leaves. In some areas there is a municipal leaf dump with leaf mold free for the hauling or you can easily make your own beginning this fall.
Cocoa shells are expensive and can be difficult to find for sale. They are light weight so they will sometimes float or blow away, and some pets seem attracted to eat them. Generally this is used as a specialty mulch or in areas where it is readily available. In my experience it is not the best thing to use in a general landscape application.
There are mixed opinions about the rubber mulch in terms of its long term effects on the soil, including possible issues of leaching heavy metals as well sometimes having sharp bits of metal in it from the tires, along with possible susceptibility to fire and odors in hot weather. Since it does not feed the soil in any way, I do not recommend it.
I hope this helps.
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