In Nemo, you can press space bar and quick look an item. For source codes, this doesnt work well because the stock Nemo preview popped up window's background is white, making it extremely difficult to see syntax highlights (white background, and blue/red/yellow syntaxes). Is there a way to change this? I am not talking about the background of the file browser. That, you can change by applying themes (I am on Mint 18.3). With themes on, the preview popped up window's background is still white.