Mathematica Black Hole shadow temperature profile

[djymndl07]

I am not sure if it is right to ask this question or not. Kindly let me know if it isn't. Actually I was going through the article Shadow Thermodynamics. I was trying to recreate the image fig 5 and 6 in mathematica. The idea is that we have to draw circles of radius $r_s$ given by equations 16,18,24,25 over a certain range of $r_h$ and the bar legend showing corresponding temperature in equation 19. I can create fig 5, though not exactly matches with the article but I cannot make fig 6. Can anyone help me with this? At least tell me the color function and scaling idea used in this paper.
Thank You in advance