You can change colors of any cells of palette (in 8bpp mode). For it you need to move frame-cursors to colors and press 'Left Softkey' with text 'Edit'. Edit-color-mode window will be opened, when you can setup R,G,B components values for these colors (from 0 to 255 for R,G and B, using button 1-3 for R, 4-6 for G, 7-9 for B). You can see name of color you edit now at the bottom (FC or BC), you can switch it with 'Joy' or 'JoyUp' button.