Listing Values, Columns Axis

Columns don't have values. They have row numbers (or indexes) which then point to cells that have values.

To swap columns and rows you can use Pivot/unpivot transforms. 

You would  need to run a custom function that identifies the names of the columns containing cellse with the value "green".

Then you would do a SelectColumns against that list

Then you would do the pivoting thing to swap rows and columns.

Now the question is - how many rows does your table have?  This might be fine for 20 rows, but will certainly not work for millions of rows.