Work around for styling colour not working for formulae with html

I have formulae which are hidden by styling to blend in on TABS regardless of colour.

Even a formula on a non coloured TAB is visible if the styling does not 'take' due to html in the formula in 3.13....  The formula however does have a colour which is #f7f8fc.

To get around the styling 'bug' I have started colouring the TAB and the border of the formula with #f7f8fc as the custom colour.

Maybe some folks will find this helpful.