Synced pattern title illegible when using block-based theme with dark background

[dcalhoun]

Description

When using a block based theme that includes a dark background color, the title and help icon of a Reusable block is very difficult to read.

Step-by-step reproduction instructions

1. Set a site's theme to a block-based theme with a dark background, e.g. Geologist.
2. Add a Reusable block to the block editor canvas.

Expected behaviour

The Reusable block title and help icon are legible.

Actual behaviour

The Reusable block title and help icon are illegible due to the low contrast ratio.

Screenshots or screen recording (optional)

WordPress information

• WordPress version: WordPress.com
• Gutenberg version: v12.0.1
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? No, Geologist.

Device information

• Device: iPhone 13 mini
• Operating system: iOS 15.1.1
• WordPress app version: v18.8