Okay lets get dangerous, creative or both.
Our lettering instead of being inset with light emitting material would instead be a window to an internal light source.
The outer shell gold or better yet a gold toned Titanium alloy.
The window laser cut and filled with a transparent yet durable material. Transparent Aluminum?
We will need an orange or red-orange phosphor of reasonable brightness.
I remember the older CRTs used orange phosphors and they had good brightness.
Now to get the phosphor glowing without the use of an external power source requires some low energy Beta particles.
Beta particles - Electrons from nuclear decay instead of a chemical battery or a glowing tube filament.
Tritium is relatively safe though the half life is about 12 years and it would need to be incorporated as a plastic with the phosphor.
Nickle with a 100 year half life would be better but I am not sure about the energy levels being compatible.
Mind you it is a metal and wont compromise the rings strength.
Now to make the whole thing body heat reactive we will add another layer to act as a shutter.
Good old liquid crystals react to changes in temperature by twisting.
The twisting changes their molecular structure, which alters the wavelengths of light or colour that is reflected, absorbed or transmitted.
Looking this over I think it can be done with some very basic engineering.
Hey right up Union Robotics alley for both creativity and engineering.
Even I want one now
Can anyone make it so?