How to theme the reference popup window in the VS Code editor - visual-studio-code

Question

I'm creating a custom colour theme extension for Visual Studio Code and I can't find out how to customise the colours for certain parts of the user interface. The theme is complete, apart from customising the reference popup window.
Here is the popup window I'm trying to customise:
I wish to change the blue background and if possible, the blue border lines. I'm sure this can be done because some of the built-in themes do so. Does anyone have an idea what I would need to put into the colour theme file to achieve this?
I'm also looking for pointers to customise the status bar colour (at the base of the editor).

Answer 1

As far as I know, this is not possible.
Some of the built-in themes are build differently. Most themes are textmate style themes, but you can see here that some of the built-in themes are .json files and are somehow handled differently.
You can find the theme documentation here. Specifically, this part is relevant:
Besides the TextMate language grammar standard scopes, VS Code also
has custom theme settings which you can use to tune your own theme:
rangeHighlight: Background color of range highlighted, like by Quick open and Find features.
selectionHighlight: Background color of regions highlighted while selecting.
inactiveSelection: Background color of selections when not in focus.
wordHighlight: Background color of a symbol during read-access, like reading a variable.
wordHighlightStrong: Background color of a symbol during write-access, like writing to a variable.
findMatchHighlight: Background color of regions matching the search.
currentFindMatchHighlight: Background color of the current region matching the search.
findRangeHighlight: Background color of regions selected for search.
linkForeground: Color of links.
activeLinkForeground: Color of active links.
hoverHighlight: Background color when hovered.
referenceHighlight: Background color of a reference when finding all references.
guide: Color of the guides displayed to indicate nesting levels.
You can find an example VS Code theme here which includes the custom
settings.
As we can see here, there is no special override for the references pane.
We can, though, see in the code that the dark blue for dark themes and the light blue for light themes that you're seeing in the references pane is a default value set in code here.

Answer 2

The colours for the UI itself are stored in the following file (ubuntu): /usr/share/code/resources/app/out/vs/workbench/electron-browser/workbench.main.css
You can edit that, or wait for March 2017 where a new version will be released which will allow customising these colours more easily.

Answer 3

Revisiting this in Sept/2022 out of necessity, I confirmed VS Code 1.70 has native support for manipulating colors for the Go to References/Definitions and Peek... overlays.
Change the overlay background and border as follows, but there's lots of other settings too; see peekView*
"workbench.colorCustomizations": {
"peekViewEditor.background": "#01041a",
"peekViewResult.background": "#054c8a",
"peekView.border": "#04fafa"