Change details of view rule style used on Dashboard (or make new style)

I have a dashboard that needs to display rows with a red background, but the setting style “Error” is too dark.

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Where do I find the definition of the “Error” style, to make it a lighter shaded of red?

Or ideally … Can I define a new style and choose it in the Dashboard developer, such that it appears in the dropdown shown below?

If you do figure this out, let me know. I would love that as well!