1) What inspired this wish list request?
In GraphBuilder, one can drag a column onto the Color drop zone to use different colors woth the individual items in the column - or to apply a color gradient depending on the values of this column.
By dragging 2 columns into the color drop zone, one can provide 2 columns -and then later specify via the variables list which of the two columns to choose.
This makes it possible to apply independent color settings to different subplots, like in Graph-Builder-subplot-with-different-color-settings
Unfurtunately, dragging more than 2 columns into the column drop zone doesn't work - just the first two will get there.
But JSL scripters have "luck" *):
via JSL one can specify more columns
Color( :col1 ),
Color( :col2 ),
Color( :col3 )
and the columns also show up in the variables drop zone.
(story continues @ 3.)
2) What is the improvement you would like to see?
Please allow the user to drop more than 2 columns onto the Color drop zone.
And much more important:
Please make GraphBiuilder handle more than 2 Color columns correctly.
3) Why is this idea important?
*) Actually, JSL scripters are not much luckier than GraphBuilder users - neither of them has a chance to use 3 different color settings in one GraphBuilder graph:
Unfortunately, the third color column doesn't work.
It's there, it seems to work, but it doesn't do what it should do.
The below code intentionally uses sex twice as color (1. and 3. entry).
This is not the reason why it doesn't work - it just helps to illustrate the issue.
A comparison of the top and bottom plot shows that the top plot (which uses the third color column) has wrong colors (no blue points, the points are red) 
In different examples, the second color column was used instead of the third one.
Names Default to Here(1);
dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
Graph Builder(
Show Control Panel( 0 ),
Variables(
X( :height ),
Y( :weight ),
Y( :weight ),
Y( :weight ),
Color( :sex ),
Color( :weight ),
Color( :sex )
),
Elements( Position( 1, 1 ), Points( X, Y, Color( 3 ) ) ),
Elements( Position( 1, 2 ), Points( X, Y, Color( 2 ) ) ),
Elements( Position( 1, 3 ), Points( X, Y, Color( 1 ) ) )
)
