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

Let's just clarify what you want to do exactly.

For counting cells of a given colour, non-blanks are worth 0.5 and blanks 0 ?

For summing cells of a given colour, non-numerics worth 0

I'm heading off line, assuming prior post is correct then below is the original condensed and altered.

Function ColorFunction(rColor As Range, rRange As Range, Optional SUM As Boolean)
    Dim rCell As Range
    Dim lCol As Long
    Dim vResult
    lCol = rColor.Interior.ColorIndex
    For Each rCell In rRange
        If rCell.Interior.ColorIndex = lCol Then
            If SUM Then
                vResult = WorksheetFunction.SUM(rCell.Value, vResult)
            Else
                vResult = vResult + IIf(rCell.Value <> "", 0.5, 0)
            End If
        End If
    Next rCell
    ColorFunction = vResult
End Function

Though FWIW IMO it is ill advised to differentiate / calculate based on "feel / appearance".

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.