Calendar block: difficult to read when background color is dark

[worldomonation]

Steps to reproduce the behavior

1. Start a new post.
2. Insert a Group block.
3. Select the Group block.
4. From block options, change the background color to something dark eg. 0x000000

What I expected to happen

Text color of the Calendar block changes to show white outline at some threshold.

What actually happened

Text color remains the same as when the block was inserted, a grey-ish color.

Notes

This issue is not reproducible with Jurassic Ninja site.

Context

Back to Basics user testing.

Browser / OS version

OS: macOS Big Sur 11.1 (20C69)
Browser: Firefox Nightly 87.0a1

Is this specific to the applied theme? Which one?

Any theme.

Does this happen on simple or atomic sites or both?

Tested on Simple.

Is there any console output or error text?

No.

Level of impact (Does it block purchases? Does it affect more than just one site?)

Minor/Moderate - prevents users from using dark color background well. Makes the calendar text quite difficult to read.

Reproducibility (Consistent, Intermittent) Leave empty for consistent.

Consistent.

Screenshot / Video: If applicable, add screenshots to help explain your problem.

[simison]

@jeffikus @scruffian hi! does this seems like a theme issue or core issue to you?

[scruffian]

It's a core issue. We have a couple of PRs open for it:
WordPress/gutenberg#29731
WordPress/gutenberg#29714