Mr Color RLM 81 is not even close. RLM 83 is to dark. RLM 76 to blue = pretty much RLM 65. 74,75 are ok, Haven't seen 82.
I believe that Mr Colors are LACQUERS. They require different thinners than TAMIYA ACRILICS.
The same goes for AK Real Colors series, all Lacquer paints. You have to use Mr.Color Leveling Thinner 400, or just Thinner 400.