Hi! Welcome to the Samsung Members community!
The best way I would suggest is:
Download the "Good Lock" app and go to "Theme Park."
Once there, go to "Themes," create a new one, click "Next," and click the second one from the bottom row. Change the colors to what you want, making sure they are easy to read. Click/ swipe Back, and then click the save icon in the top right (download folder icon). Name it; it will bring you back to themes, and you should notice the one you created. Click it and let it load. Done.
The best way I would suggest is:
Download the "Good Lock" app and go to "Theme Park."
Once there, go to "Themes," create a new one, click "Next," and click the second one from the bottom row. Change the colors to what you want, making sure they are easy to read. Click/ swipe Back, and then click the save icon in the top right (download folder icon). Name it; it will bring you back to themes, and you should notice the one you created. Click it and let it load. Done.
Hi @LMD26 Welcome to the Samsung community 
This can be due to a theme so try changing as mentioned or set a Default via Settings-Themes. I would also ensure that Vision Enhancements are switched off,Settings-Accessibility-Vision Ehancements.
