Count coloured cells - But treat cells with colour and value as 0.5

Non blanks are worth 0.5 and blanks are worth 1

Change the 0 in the IIF to 1.

usings colours to display holiday days - And text within that colour to stipulate half a holiday day

Would be better to use H (or 1) in cell to denote Holiday and HH (or 0.5) for Half Holiday - use Conditional Formatting to apply colour based on the cell value if required. No VBA required from that point forth.