I would suggest that we keep the same colour for the quote, but instead just add the rule along the side.
I took the line colouring from the yelowyellow one on Meta.SE- it goes from (33,255,241) to (35,255,199), a change of (2,0,-42) so I did the same with the grey, from (0,0,238) to (2,0,196). These are all HSL colour numbers.
I also think that the code should change colour, maybe to be slightly darker than the quote, so that you can see a diferencedifference when there is quoted code:
This is a quote.
This is embedded code
. Not much difference.
The embedded code background is #dcdcdc. This could possibly only happen when it is embededembedded in quotes? But a permanent change wouldn't be bad.
My pronouns are He / Him