I have used the following public function (thanks to David Lean) to show a Excel like Red Yellow Green color scale to a text box value based on a minimum and maximum value.

Code:
       Public Function ColorRYG(ByVal Value As Decimal, ByVal MaxPositive As Decimal, ByVal MaxNegative As Decimal, ByVal Neutral As Decimal) As String
    'Example: =code.ColorBack(expression, Max(expression), Min(expression), 0)
    '=code.colorback( Fields!Sales.Value,max( Fields!Sales.Value),min( Fields!Sales.Value),0)
    'Find Largest Range
    Dim decRange As Decimal
    Dim decPosRange As Decimal = Math.Abs(MaxPositive - Neutral)
    Dim decNegRange As Decimal = Math.Abs(MaxNegative - Neutral)

    decRange = IIf(decPosRange > decNegRange, decPosRange, decNegRange)

    'Force color into Max-Min Range. Important if you want to Clip the color display to a subset of the data range. 
    Value = Switch((Value > MaxPositive), MaxPositive, Value < MaxNegative, MaxNegative, True, Value) 
    'Find Delta required to change color by 1/255th of a shade
    Dim decColorInc As Decimal = 255 / decRange

    'Find appropriate color shade
    Dim iColor As Integer = CInt(Math.Round((Value - Neutral) * decColorInc))

    'Return Appropriate +ve or -ve color
    Dim strColor As String
    If iColor >= 0 Then
        'Green
        iColor = 255 - iColor 'Thus 0 = White & 255 = Green
        strColor = "#" & iColor.ToString("X2") & "FF00"
    Else
        'Red
        iColor = iColor + 255  'NB iColour is -ve;  -1 - -255 
        strColor = "#FF" & Math.Abs(iColor).ToString("X2") & "00"
    End If
    Return strColor
End Function

I then use the following expression in the textbox :

=code. ColorRYG(Fields!BlokkeklaarPersentGelewerKultAliasnaam.Value,max(Fields!BlokkeklaarmaksimumKultAlias naam.Value),min(Fields!BlokkeklaarminimumKultAliasnaam.Value),0)

However when I run my VB.net application I only get the hex value of the color and not the actual color in the text box.

Any help would be much appreciated.
Regards