Does anyone know why in some viewer pictures after processing with LR change colours?

[#1]

[#2]

[#3]

First, is this a Lightroom Classic question?

Most likely, your monitor is not properly calibrated, or you are using a viewer that is not color managed. What viewer are you using?

To see if your monitor is properly calibrated: https://www.lightroomqueen.com/how-do-i-change-my-monitor-profile-to-check-whether-its-corrupted/

[#4]

It would help if we knew what you were comparing (i.e. what applications are displaying the image, is it the same image, etc.). Some viewers are color managed and some are not. When asking questions in the forum, it really helps when you can provide as much information as possible.