How do I get my firefox appearance back to the original look, I am having difficulties in seeing certain buttons and it is causing me to make a lot of mistakes

A lot of the "submit" buttons are no longer highlighted, and other buttons too. The blue is no longer a nice rich deep blue. Hyper text is not a clear as it used to be. Sites that were visited previously aren't the same color. I just want to go back to the original classic Firefox look that I've for years. I'm having the same issue with my computer at home. Something happened during the last Firefox update