One method is simply to create an array with color names and use that in palce of integers:

@color = qw|red green blue|;

$can->create ( 'rectangle',
        $X,   $Y, 
        $X+1, $Y+1,
        -fill => $color[1];
    );
[download]

To set your whole application to a consistent color, use

$widget->setPalette('red');
[download]

You can also the hex values in place of a color name:

($r, $g, $b) = $widget->rgb("red");
$hex_color = "$r$g$b$";
$mw->Button( -background => $hexcolor);
[download]

-Mark