@"KarenP"
Also try disabling font anti aliasing.
After each major os update, I make sure this is disabled (last two releases did not honor my setting and had reversed it)
# check current val
defaults -currentHost read -g AppleFontSmoothing
# if it's not 0, then set it to it and reboot
defaults -currentHost write -g AppleFontSmoothing -int 0
"0" disables font smoothing
"1" enables light font smoothing
"2" enables default medium smoothing
"3" enables strong smoothing.
PS: if the write command fails, add "sudo" in front