Data Lineage SelectOnlyC2 error

Dear Power BI Representative,

I am reviewing Chapter 14 of The Definitive Guide to DAX and in the 'Understanding data lineage' section I was running the following code in DAX Studio as directed.  However for some reason the SelectOnlyC2 variable DAX is not able to find C2 even though variable AddC2 is recognized if one sets the RETURN to AddC2 for testing.  The error I received was 'Query (18,34) Column 'C2' cannot be found or may not be used in this expression.'  Why is DAX unable to find C2 for the SelectOnlyC2 variable?  Your insight into this matter is much appreciated.

Thank you.

DEFINE

     MEASURE Sales[Sales Amount] =     

         SUMX ( Sales, Sales[Quantity] * Sales[Net Price] )

EVALUATE

VAR NonBlueColors = 

    FILTER (

        ALL ( 'Product'[Color] ),

        'Product'[Color] <> "Blue"

    )

VAR AddC2 = 

    ADDCOLUMNS (

        NonBlueColors,

        "[C2]", 'Product'[Color]

    )

VAR SelectOnlyC2 = 

    SELECTCOLUMNS( AddC2, "C2",[C2])/*issue with this formula, DAX is not able to find C2.*/

VAR Result = ADDCOLUMNS ( SelectOnlyC2, "Sales Amount",[Sales Amount] )

RETURN Result

ORDER BY [C2]