This is that RED that you have been looking for!  Functioning thermometers are set in sterling silver. Temperature range registers from -140 F to +120 F. When the sun shines on one side of your head, check out the difference, but keep your eyes on the road!  Complete length from the earlobe is 2" (54mm).

Technically these are "thermoscopes"- they register a change in temperature without an actual numerical value associated with it.  One side of the settings is marked with fahrenheit, and the other side is celcius. There is a little red mark at 68'F for your reference.