Here is my second Essence thermal polish (at present the Thermo polishes are a Müller exclusive): n. 04 The heat is on. The shade goes from cherry (warm) to black cherry (my cooler tips, in these pictures); the difference is noticeable, although not flashy.
The polish is really easy to apply, two "quite thick" coats in my pictures, as you can see the surface is perfectly covered -not patchy-, but still a little bit see-through (almost jelly).
Again, a polish I'll be happy to wear also when the termal effect will be over.
Technical note on thermal polishes: color change won't happen forever (some retailers declare a "one year shelf life" for them). Proper storage is important to make them last as long as possible (eventually the darker color might prevail). It's better to avoid UV exposure and high temperature (don't leave them under the Summer sun in your car, for instance), so I'd recommend keeping them in a cool place.