From what I can tell it's a tinted cement binder so I guess there's some dye involved but given the various colors of the pebbles, it's not a uniform finish in the first place and I'd assume mottling wouldn't be as big of an issue (depends on how much of the color comes from the tint vs the pebbles). Spend some time with google looking for "pebbletec mottling" and you may get more results. The initial stuff I found indicated it to not be a problem but I'm not sure if it's the same for pebblesheen (which is just smaller pebbles that are polished). Ignore their pebblefina since AFAIK it's not a real exposed aggregate like the others.