From GeoGebra Manual
- DynamicCoordinates[ Point A, Number X, Number Y ]
- creates a point with coords (X, Y). This point is dependent, but can be moved. Whenever you try to move the new point to coordinates (x,y), point A is moved there and coordinates for the new point are calculated. Works best if point A is not visible. At least one of X and Y should depend on A.
- Create three slider a, b, and c with an interval from 0 to 1.
- Create a polygon whose color should be influenced by the slider values.
- Open the Properties Dialog for the polygon poly1 and enter the names of the three sliders into the text boxes for the color components.
- Close the Properties Dialog and change the values of the sliders in order to find out how each color component influences the resulting color of the polygon.
Note: You could also animate the sliders with different speeds in order to see the color of the polygon change automatically.