Photoshop :: Selective Color Too Pale/washed Out

I'm running photoshop CS3 in a macbook pro under windows xp, and I want to add color to something in my picture. I used "selective color" (Layer > adjustments > selective color) to add color to a whitish-looking robe that is worn by a character that I created in photoshop earlier, but even when I move the slider to +100 % the color is still too washed out (will add images later). I know from experience using Photoshop CS 3 in my old laptop (a HP Compaq Presario X6000 running windows XP)  that to get the depth of color I want in my character's robe, I shouldn't have to move the slider all the way to +100 %. Is there any way to fix this so I can get the same color depth I got when I used my old laptop? P.S. When I choose "selective color" a dialogue box comes up. I left the settings in this dialogue box as they are seen in the image, and clicked "ok".