Using Linux Mint Cinnamon, I blocked out the following lines in the "/usr/share/gtksourceview-3.0/styles/cobalt.xml" which eliminated my problem. If this would have been helpful, my apologies for not posting this solution ``` <!-- Bracket Matching <style name="bracket-match" background="steelblue3"/> <style name="bracket-mismatch" background="dark_red"/> --> ```