- Refactors the UI controls around the Iris color picker to output valid and semantic markup
- Simplifies the way elements visibility gets toggled
- Properly associates the visually hidden label with the color input field
- Makes the toggle button a real button
- Adds `aria-expanded` to the toggle button
- Keeps focus on the toggle button instead of moving it to the color input field
- Adds `aria-label` attributes to give better context to some controls
- Removes a redundant title attribute
- Keeps the toggle button text to "Select Color" instead of changing it to "Current Color" when a color is selected
- Slightly improves the responsive view
- CSS clean-up
Fixes#39662.
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