Include a feature for all pro users to change/customise the background and colours of days for past, present and future day for all themes.

At present, only the next month and present day background colour can be colour customised, not including days left in the current month, where viewers can be deceived as the rest of the days left in the current month background colour/shade cannot be changed/customised in the pro version and it looks out of place.

Note:
These changes/customisations to include colour customisations as well for all themes and their backgrounds in the pro version only.