lightroom classic. In masks every time I make a selection it is in blue and yellow

Your screenshot shows that ‘Reset sliders automatically’ is unchecked. That means each new mask gets the same settings as the last mask you used. In your screenshot we can only see that this includes Shadows=+1, but kind of the color grading as shown on the dog would obviously be in other panels, that are collapsed.

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1. In the Mask panel, check the option Reset Sliders Automatically. Then create new masks -- does the problem still occur?  Your screenshot shows the only changed slider is Shadows = +1. But do this just to verify.

2. To the right of Show Overlay, click the green box and select red as the overlay color. Do selected objects now get highlighted in uniform red?

3. If steps 1 and 2 don’t help, please do the LR menu command Help > System Info, click the Copy button in the upper right corner, and paste into your reply here, so we can see exactly which versions of hardware and software LR thinks you're running and important LR options that are set.

In addition to ​@JohanElzenga ‘s post try to reset the preferences of Lightroom Classic:  How to reset Lightroom Classic preferences (adobe.com)

It's recommended to backup your preferences before you reset the preferences to the default settings: https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html

Post a screenshot please. You can set the mask overlay to a different color, but then one would expect just a single color, not blue and yellow. Another possibility is that ‘Reset all sliders’ got unchecked in your mask panel, so this is something you used previously, which now gets applied to all new masks.

BTW, Lightroom Classic questions should be asked in the Lightroom Classic forum, not in the Lightroom ecosystem forum. Expect a moderator to move your thread.