Test: Improve the 'DOM element should have a CSS filter close enough to hex color' filter

[abias]

Every now and then a Behat run fails with an error like this:

001 Example: | communication      | choice  | #0000FF  | invert(0.48) sepia(0.74) saturate(48.87) hue-rotate(11deg) brightness(1.02) contrast(1.01)  | # /home/runner/work/moodle-theme_boost_union/moodle-theme_boost_union/moodle/theme/boost_union/tests/behat/theme_boost_union_looksettings_activitybranding.feature:34
      And DOM element ".chooser-container .activityiconcontainer.modicon_choice img" should have a CSS filter close enough to hex color "#0000FF"      # /home/runner/work/moodle-theme_boost_union/moodle-theme_boost_union/moodle/theme/boost_union/tests/behat/theme_boost_union_looksettings_activitybranding.feature:26
        The '.chooser-container .activityiconcontainer.modicon_choice img' DOM element with the CSS filter 'invert(0.11) sepia(0.94) saturate(53.67) hue-rotate(243deg) brightness(0.89) contrast(1.54)', is not close enough to the color '#0000FF'.

This step is used to check if the CSS filters which are applied to tint the activity icon colors are fine or not.
Re-running the scenario mostly always fixes the problem - or it occurs again with another filter given.

However, if you look at the generated CSS filter, the color is indeed close enough:

So I expect that the Behat failure is a mathematical problem, not an optical problem with the colors.