Palette Pal is an web-based tool for creating 256-color palettes by Adam Perry/Mogri and available here.
Here's how it works:
- Generate your initial palette using the settings you like. As you go, you can use the Save/Load buttons to keep ones you like. (Your palettes are remembered even if you close the browser and come back, as long as you're on the same computer.)
- Once you have something you're happy with, you can start hand-editing your palette. Start by clicking on one end of a color ramp and dragging to the other end. This will highlight the selected colors and open a new menu.
- The new menu allows you to specify a start color and an end color. You can do this in RGB or HSV, whichever you prefer. After tweaking the colors, click the Ramp It Up button to alter your palette. You can use the Copy/Paste buttons to store the values in the form and paste them onto a different ramp.
Color selection is freeform, so you can highlight multiple ramps or part of a single ramp. But once you click on the Ramp button, the selection is treated as a ramp, regardless of the size of your selection.
There's no way to download the resulting palette as a file. Instead, take a screenshot of the window and use the 'crop' tool in a graphics editor like Paint to cut out the little 16x16 image of the palette. Save this as a 24-bit .bmp file and you'll be able to import it into Custom.