On website, the edition is done in an iframe while the SnippetsMenu
resides outside of said iframe. This means that the SnippetsMenu no
longer has frontend styles. Therefore, colors aren't accurate.
This commit aims at patching web_editor widgets, such as color_palette,
so that the color displayed is always accurate. To do so, it computes
the color inside the iframe and adds style attributes to color_palette
preview elements.
See merge commit for more information.
task-2687506