You can already do that: in the settings.json under workbench.colorCusomizations, change editorBracketHighlight.foregroundX where X is the level of bracketing y

You can already do that: in the settings.json under workbench.colorCusomizations, change editorBracketHighlight.foregroundX where X is the level of bracketing you want to modify. In practice, though, the reduced color vision combined with the small target that is a bracket (color vision degrades for smaller objects), means that this is of limited usefulness.