As I look back at the reference picture of the Carbonite chamber, there is a second circle in the back as well that is exactly the same yellow-orange color as the neighboring rings. So I am not very happy with the base:
#1) I think the bases ARE supposed to be the same color.
#2) The scale of the oblong slots is VERY different. The width of the slots of both bases should be the same.
#3) The Han Solo base is shiny black and the Boba Fett is Flat Black. They should be the same.
#4) The black flooring of the Han base is 1/2" thick, and the Boba Fett is 1/8" thick.
Take a look:
View attachment 456189
Here is the original advertisement picture which shows bases with the same color and scale:
View attachment 456190