What's the secret to getting Link Colour to appear?

[bobbingwide]

For both the Post Edit block and the UK tides block I want to be able to customize the foreground and background colours for both the text and the link. Getting the Link Colour settings pane to appear is not an easy task.
It appears for Fizzie and ThisIs, both using Gutenberg, but not for other themes.
What's the secret?

Colour settings for the Post Edit block using the ThisIs theme. ( WP 5.7.2 GB 11.0.0 )

Colour settings using the Fizzie theme ( WP 5.7.2 GB 11.1.0 )

[bobbingwide]

I understand it's to do with theme.json.
By default settings.color.link defaults to false for both FSE and normal themes.
If you set it to true then the Link Colour settings should appear.
Note the inconsistent capitalisation of Color/Colour in this panel.

[bobbingwide]

It works for Fizzie, ThisIs..., Wizzie and Written. Can't test with SB at present.
It doesn't appear to work with other themes with WordPress 5.8.

Oh, it's working now in s.b/wordpress with the oobit theme with theme.json set to:

{
  "version": 1,
  "settings": {
    "color": {
      "link": true
    },
    "spacing": {
      "customPadding": true
    },
    "typography": {
      "customLineHeight": true,
      "fontFamilies": [],
      "fontSizes": []
    },
    "layout": {

    }
  }
}

but NOT in s.b/cwiccer with the same theme!

[bobbingwide]

but NOT in s.b/cwiccer with the same theme!

Oops, oobit in cwiccer was old. It wasn't symlinked. So there was no theme.json.

[bobbingwide]

Env	Gutenberg version	Theme	Colour fields available?
s.b/wp55	14.5.0	ThisIs	Background, Link
s.b/wp55	14.6.0	ThisIs	Background, Link
s.b/wp55 & sneak-peek.me	14.6.1	ThisIs	Background, Link
s.b/wp55	14.7	ThisIs	Background, Link
s.b/wp55	14.8.4	ThisIs	Background, Link
s.b/wp55	14.9.1	ThisIs	Background, Link
s.b/wp55	15.0.0	ThisIs	Background, Link
s.b/wp55	15.0.1	ThisIs	Background, Link
s.b/wp55	15.1.0	ThisIs	Background, Link
s.b/wp55	15.1.1	ThisIs	Background, Link
s.b/wp55	15.2.0	ThisIs	Background, Link

• In sneak-peek.me the Text color was also displayed.
• The results for s.b/wp55 reflect the newer settings in block.json where text is set to false.

"color": {
	  "gradients": true,
	  "text": false,
	  "background": true,
	  "link": true
	},

• We don't need text since the block only displays a link.
• From GB 15.1.0 the styles appear in a separate tab.
• In GB 15.2.0 there are more panels for Typography, but not Dimensions.
  

For reference see https://developer.wordpress.org/block-editor/how-to-guides/themes/theme-json/