The palette that is located in the Home tab in the top menu lets you colorize your selected object(s) with a single click on the color you want.
At the top right of the palette there is a multi colored square that lets you select between the different palettes that exists in the system. There are a number of palettes delivered with DISE and you can easily add your own. DISE Composer will remember which palette you were using when you close the application and show the same palette when you start again.
To the left of the palette, there is a slider that lets you select the opacity of your selected object(s) (Alpha).
The number of colors in the palette is 16. If you are running the editor at low screen resolutions, all the colors might not be shown. If this is the case, the palette can be resized to give you more columns.
Detailed settings of the colors can be done on the Color settings tab in Object Properties.
Note: If you are working with gradient objects, a "hidden feature" of the color palette is to hold down the SHIFT key while selecting a color. The selected color will then be the second color in the gradient instead of the first one.