As far as I know blue dots are illegal every where. DOT reg. that the brakelights should be red only and so much of the lens should be reflective.
Keep in mind each juridiction has their own respective ordinances too. Where I worked, items hanging from the rear view mirror, cracked windshields, nonfactory or modified exhausts, any lights on the vehicle other than those that came on the vehicle (i.e. accent lights under vehicle), window tint on driver's or passenger side, were all violations of city ordinances. That doens't mean guys would write such chicken**** violations, but it is good to know such ordinances so when you come across those that you know are good for "other" things you have the ability to come up with p.c. for a stop.