Mysterious changes to standard color palette

Hi Everyone,
I am using Excel 2010. Periodically, I experience an issue where the standard colors in Excel's color palette will change, and subsequently, any file that I open which uses one of the affected standard colors, will appear different. I am almost certain that the behavior occurs after opening emailed files coming from another company, and/or copying and pasting from those files into my files. It seems inconsistent and I haven't been able to narrow down exactly what file or action is causing the issue. Once it appears, it affects every file that I open. The only fix I have found is to open a new instance of Excel, or completely close the affected instance and reopen Excel. Both of those will reset the standard colors and my files appear normal again, however, this is a pain when you have a dozen or more large files open and need to close out of every one and reopen just to get the colors back to normal. I've been dealing with this for years and have begun looking into it more. I've seen similar issues described in the forums, but none with a solution that has worked. It happened again today, so I grabbed some screenshots.

Here is a screenshot showing the standard colors after the issue occurred:
Messed up colors.jpg

I opened a second instance of Excel and took this screenshot of my normal Excel colors.
Normal colors.jpg

You can see that a few colors changed or shifted places, and those are the same changes I am seeing in my files (ex: cells using the standard blue font color all turn to ivory when the issue strikes)... until I close Excel completely or open a new instance. Does anyone know what is causing this, or a way to reset the colors easily without closing Excel or changing them one-by-one?

I could be wrong, but this could be due to changing the color scheme theme in Excel. This is located on the Page Layout Ribbon > Colors drop down. (highlighted in yellow below)

Thanks, but I checked that and it is still set to the original "Office" and looks the same as my new/good instance of Excel.

Colors.jpg

UGA;

the original color palette screenshot you posted in the original thread, how do you get to that dialog box? I am working on EXCEL 2016 and i can't find that exact screen.

One interesting thing... if I go to the Colors screen that I provided in my first screenshots, and I modify the affected colors to put them back to what they were originally, it fixes the files... but then if I go back to that screen and click "Reset", it puts them back to the altered/incorrect colors. So something is altering what Excel thinks is the standard/default color set since "Reset" is also undoing my changes (changes that put it back to what I see in a new/unaffected instance of Excel). So I'm wondering where Excel is getting the defaults that it uses with that "Reset" button. Somehow those seem to be changing.

Originally Posted by dosydos

UGA;

the original color palette screenshot you posted in the original thread, how do you get to that dialog box? I am working on EXCEL 2016 and i can't find that exact screen.

It's under File-->Options-->Save-->then at the bottom click "Colors...". Not very intuitive since you don't have to actually save the file to see the changes take effect. I think Colors used to be in it's own section in older Excel versions, but at some point, they grouped it under the Save settings.

I believe it's in the same place in 2010 and 2016 though.