Since 3.5 you can change the color
edit>preferences>themes>3d viewport>camera passepartout
Hello,
I was wondering if there is a option for the color off the passepartout in the camera menu. I could not find a option in the themes. The reason is that I often print my work on paper and would like to have a white background in the the preview
I’m not sure I understand what your problem is. Once rendered, an image shows no passepartout, just the area inside it.
Do you mean that you often print your work in the paper with Blender UI?
Thanks for replying, I do not print images with the UI
Its just for having a similar background color in as the final print in the preview.
At least I think images are perceived slighty differently depending on the backround color
You cannot change the colour but you can fake it if you want to make the effort
Have a white plane with a hole just in front of the camera parented to the camera and have a track to constraint so it always faces the camera object.
or set the background colour to white and turn off the passepartout
Hi folks,
7 years later, is it still not possible to change the outside color, as the OP asked?
I’m often working with a completely black world color and i’d like to be able to change the outside color without needing to resort to hacky workarounds.
Any ideas? … Thanks!
Have not found anything. Had no success finding some easy value change in the source code, also tried it on right click select. Dont see a reason why this part of the UI has no option for changing the color
That is a pertinent request to be able to have this, as a white or grey color instead of black one.
A Camera Passepartout color was added to theme of Viewport, for 3.5 , yesterday.
thanks for the info, thats great news. Stil could see a use for having a color picker at the same location as the passepartout transparency setting, since it can be project dependent, but this will do for now.
Absolutely!!
If you think about it, when is the outside of the image ever pure black?
Actually, only in the cinema.
When viewing the final result on a computer monitor or TV, you have a wall or your room behind the image (screen), or if not full screen, then the rest of the web page.
On mobile, you have your physical hand outside the frame.
In print, you might have some other design element apart from white.
So in fact, apart from a color picker, with also need the option to add an image to the passpartout area that can be set to either a fixed size or to scale along with the frame of your camera view.
If possible, could someone please pass on my comments to the devs? 
Not wishing to sound ungrateful, but if someone is gonna fiddle with this after so many years, might as well do it right?!
Well. Color Picker is only working inside the same window.
If you open Preferences by using Edit menu or F4 menu, that will not work.
But if you switch an editor area to display Preferences instead of Properties Editor or Outliner or Timeline, you will have Camera Passepartout color field in same window as 3D View or Image Editor.
And in that case, you can use color picker.
Whoever put this in is my hero! Been wanting this for ages because I do a lot of white background product work and the black passepartout is really distracting. I’ve now made it 0.8 light grey to mimic Photoshop 
