Further improvements to theming the gutter. There are now the following keys which can be set to change the color of gutter elements: Dennis Vennink

gutterDivider: Border between text view and gutter.
gutterForeground: Text color.
gutterBackground: Background color.
gutterIcons: Color of the images in the gutter.
gutterSelectionForeground: Text color for lines containing caret / part of a selection.
gutterSelectionBackground: Background color for lines containing caret / part of a selection.
gutterSelectionIcons: Color of images on lines containing caret / part of a selection.
gutterSelectionBorder: Border between selected and non-selected lines.