From the LEGO Mindstorms EV3 Software, go to the File menu and select Open Project.

Browse to the location where you unzipped the “LEGO blocks and examples” file, and then to the examples directory. Select “rgb_test.ev3” and click on Open. The program is shown below.

Run the program by clicking the play icon in the lower right corner of your EV3 software window. If you don't see the play icon, make sure your LEGO brick is powered on, finished booting, and connected to your computer via a USB cable.

Your EV3 LCD should display three circles indicating the relative intensity values of red, green and blue.

You might notice that at least one of the three channels (R, G or B) is always 255. This is because the color is “saturated” to give the most color differentiation. Notice also that the X and Y inputs are 128 and 128, which indicate the center of the image.

You can change the X and Y values if you want to get the RGB values from different locations within the image (refer to the coordinate picture below.)

RGB sensing coordinates