Thermochromic pigment that changes at around 50 °C / 120 °F? I wish to find a pigment that can indicate when a battery contact is getting too hot, and all the thermochromic pigments from hobby stores change color below body temperature, at 31 °C is the highest I found. 

What kinds of thermochromic pigment can be used for electronic components, that would change color at 40–50 °C / 120–140 °F? 

The best thing would be easily obtainable and would give an rough indication of temperature transitions from 30 to 55 °C
The easiest way to obtain such a pigment is to mix a blue and red thermochromic pigment together, one that changes at 32 and another that changes at 50 dregrees. They aren't very easy to find, for the moment i have found the 32 degrees pigments on ebay, and a 45 degree pigment on aliexpress: