[Feature Request] Inconsistency between background and border on the same element

# Feature Request

## Is this feature request related to a problem?
Some inline text elements use `background-color` and `border-color`/`outline-color` at the same time to generate a larger color box. Dark Reader should generate identical color for them under dark mode.

## Screenshots
One usage on [Wikipedia](https://en.wikipedia.org/wiki/Template:Rail_color_box):

## Additional Context
I understand that there are performance concerns for keeping such consistency if those properties are defined separately for a element, so I'm proposing this only for properties defined in the same scope (both inline style, or defined in the same CSS rule).

Start by reproducing the Wikipedia rail color box example and inspect how background-color, border-color, and outline-color are transformed in dark mode. The change is done when properties defined in the same inline style or CSS rule produce identical colors without requiring consistency across separate scopes.

Scritto dal modello di indicizzazione a partire dal testo della issue.