Colors in 3ds Max Design are interpreted in two different ways: RGB and HSV. In RGB (red, green, blue), you can select one of 256 shades of red, green, and blue, giving you a palette of 16.7 million colors (24 Bit). In HSV (Hue, Saturation, Value), you can select one of 256 hues of color, then adjust the saturation or the value of the color. The saturation can also be considered the blackness of a color and value can be considered the whiteness of a color.
For transparent and size gradients, you adjust the vertical whiteness slider just to the left of the RGB and HSV sliders. The white triangle on the right side of the vertical bar is the slider. This controls the overall value of the color in terms of HSV. In RGB terms, it is the same as adjusting all three colors equally at the same time. Higher values on the whiteness scale represent more transparency, or smaller sizes.