Environment

• Package version(s): @blueprintjs/core 5.10.3
• Operating System: Windows
• Browser name and version: Google Chrome 125.0.6422.60

Example

Link to a minimal repro: https://blueprintjs.com/docs/#core/components/form-group

Steps to reproduce

1. Enable dark theme(⇧D)
2. Enable "Show helper text"
3. Enable "Show sub label"

Actual behavior

The helper text and sub label have the same text colour when using the light theme, but a differ in text colour when using the dark theme. The sub label has very low contrast against the background.

Expected behavior

The sub label should have the same colour has the helper text, like when using the light theme:

Possible solution

Update the sub label text colour to match the helper text, like so: