Custom Chart Fill / Pattern

I am struggling to define the fill color and fill pattern of a stacked column chart. To clarify, I have one series value, and two series groupings (RepairLevel, InProcess).

In the fill color expression I have:

=Switch( Fields!RepairLevel.Value = "Major", "red"
    ,Fields!RepairLevel.Value = "Mid", "orange"
    ,Fields!RepairLevel.Value = "Minor", "yellow"
    ,Fields!RepairLevel.Value = "NA", "grey"
    ,Fields!RepairLevel.Value = "Unspecified", "light grey" )

In the fill pattern expression I have entered:

=Switch( Fields!InProcess.Value = True, "BackwardDiagonal"
    ,Fields!InProcess.Value = False, "None" )

It seems that the fill color is working properly. However, the fill pattern is not -- I am getting various fill patterns. Thanks in advance for any insights, I truly appreciate your time.