Gray?
I will leave here a screen shot my favourite themes, I made these two to fit in different situations.
Judge at will.
Ardosia 01:
I use this one when rigging and coding.I made the letters and buttons slightly brown-yelow because my eyes have tendency to see hot colors more sharply but everything else is blue-ish gray to act as hue counter so, the theme is overall neutral, so it works for lookdev too.
Dark coffe:
This theme I use when my eyes are tired or I work too long at modeling, Its the most confortable theme I ever made, I sicrified the neutrality in order to work longer when modeling, I went into a munsell test so I know brown/red are the colors my eyes can differentiate better also.