Tutorial on fixing mac blurry text for non retina external displays
Turn on font smoothing:
defaults write -g CGFontRenderingFontSmoothingDisabled -bool NOTurn off font smoothing:
# revert custom font smoothing settings
defaults -currentHost delete -globalDomain AppleFontSmoothing
# revert back to default font smoothing
defaults write -g CGFontRenderingFontSmoothingDisabled -bool YES