(photo taken from DevForums)

 I would like to address that it is possible to change your theme to a darker color, but it is not really what I was looking for. This feature is also only available if you change some XML files.

A ROBLOX Studio dark theme can be helpful and look very cool.

When developing for long amounts of time, the light specifically coming from your computer monitor can either damage or hurt your eyes.  This, of course, applies to the widgets and windows on the screen, not the game itself.

Review of Optometry states, "Just as UV light is dangerous to our skin, it's also dangerous to our eyes. So it's important that we protect them from UV damage. UV light affects the front of the eye (cataract formation), while blue light causes damage to the back of the eye (risk of AMD)....90% of all of our light sources are estimated to be LED lighting. So, our exposure to blue light is everywhere and only increasing." 

It's best for most people to try to avoid blue light, and as much as they can, especially during the night. It is also been known that blue light can cause people to have sleep problems. Even though ROBLOX Studio doesn't use as much blue light, you can see that brighter lights can also have a similar effect on people. 

There's also a nice explanation of benefits of darker UIs explained on a less-reliable source. Quora

To add on, darker UIs and themes can have even more benefits:

Source

• Eye fatigue likeliness is reduced
• Dark colors can save electricity
• Medical conditions such as photophobia as less aggravated by dark backgrounds

A lot of developers like me love that you have implemented color schemes for the script editors, but I think you should also make the whole Studio have a theme.

There have been multiple threads on the devforums stating that it is possible to change the theme by tweaking with these files, but I believe that it should be easier for everyone access this without having to go there.

ReallyExpensive