You could introduce a second element into your color.
I.e. create a calculated field called 'CurrentPeriod' as IF [Season] = 'Spring' then 'Current Period' else 'Previous Periods' END
Drag that onto the detail button on the marks card, then hover over the blank space on the left of the blue pill you've just added, click the dropdown arrow which appears and select color.
You'll then be able to apply a color to the 'Current Period' and 'Previous Periods' versions of your dimensions.
See an attached example based on the Superstore data.
colorseasons.twbx 1.2 MB