Color Picker Dialog
The color picker is divided into multiple parts, with several ways available to choose a color:
Visually Adjusting Color
The top half of the dialog consists of 2 colored boxes, one that lets you pick any point in a 256 x 256 square and the other that works as a long slider. Which colors are displayed in these two boxes depends on which radio button is selected (see below), but in all cases the position of the slider will change the colors available in the square box. Which ever point is selected in that square box is the selected color.
Adjusting by RGB or HSV
Underneath the square colored box, there is a series of 6 options (1 each for hue, saturation, value, red, green, and blue) that each contains a radio button, a slider, and an up-down number control. If one of the 3 HSV radio buttons is selected, that value will be represented by the visual slider (see above) while the other two values will be the axes of the square color box. The controls work the same way if one of the RGB radio buttons is selected. You can also adjust these values with the sliders provided next to the labels, as well as the up/down controls next to the sliders. Any adjustment of these values will update the visual controls, and any adjustment of those visual controls will update these values.
The selected color is displayed to the right of the RGB and HSV controls. The box is split diagonally, with the upper left section labeled New (the color you are creating), and the bottom right section labeled Current (the color that already exists, and will continue to be selected if you Cancel the dialog). Beneath that is the Hex Value of the selected color (you can also enter any valid hex value there to update the selected color). There is an eyedropper button to the right of the selected color that will allow you to set the selected color by sampling anywhere on the desktop.
User-defined Color Palette
At the bottom of the dialog you will find a series of 12 colored rectangles alongside a button titled Set to Swatch. These comprise the user-defined color palette, and allow you create and save (these will persist even when PhotoPad is closed) your own custom colors. To set a swatch's color, first select that swatch by clicking it. Then choose your desired color, and finally click the Set to Swatch button. You can then load any of the saved colors by simply clicking on that swatch.