What is the problem with my car in the radiator it's a yellowish milky looking gunk

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My car has a yellowish milky looking stuff coming out radiator after parking no smoke from tailpipe not overheating nor discoloration of oil that when it dries it turns purple gel type stuff, I took it to the place I always get my car serviced and was told I have a blown head gasket, and I'm not understanding how this can happen when I get my car serviced as specification of the manufacturer manual fuel flush, radiator flush ,oil changes, transmission flush and filter, and new air filters all the above by 3, 000 miles and 6,000 miles and I have 95,000 miles on it so can somebody explain this to me?