patch diamond brite pool spots?

I emptied my pool while a large tree was shedding. Cleaning it out I've found a few 12" dia.slightly raised circles that have a hollow sound. How difficult will it be for me to chop out the spots and replaster them ?and, will it show much if I use the same brand and color? or, should I just ignore them since they are in the deep end of the pool? The original finish was applied about 3 years ago. Thanks.
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