It appears that this option is no longer in it's original location and exploration has not uncovered it's new location. Did Atlassian turn off the Color options in Look & Feel?
Please see the answer here:
Long story short, you can change the global color scheme (to a very limited extent, basically only the sidebar color and background color), but space color options have been completely removed. These options are intended to be replaced by the new theming add-ons.
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