how do I add coloured text cell contents ?

[Dave P]

I would like to identify cells I wish to add together by changing the text
colour to select them, then use the sum formula to add these cells contents.

Is there an easy way to do this?

 

[Luke M]

Yes. Using color/formatting is generally to be avoided as a way of
identifying cells to be used in formulas. Instead, the simpler way would be
to place an X in a helper column (say, column Z). Then you can use the SUMIF
function

=SUMIF(Z:Z,"X",A:A)
to sum all the values in column A that have a corresponding X in column Z.

Or, if there's some rule you're using to mark the cells (such as greater
than 50, less than 100, etc) you can write that into the SUMIF function and
let it find the cells for you.
=SUMIF(A:A,">50")