crested geckos do often develop black and red spots as they get older. The black spots if there are quite a few, are often referred to as a dalmatian pattern. Red spots, providing they don't move (ie mites) seem to me to be just another coloration of random spots. There are no health concerns from these markings at all (unless they do move then they are external parasites which will need to be get rid of. However, most mite sprays are deadly to geckos...and to be honest, haven't heard of any geckos getting mites so I am pretty sure you have nothing to worry about).
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PHLdyPayne