Watch the movie:

Step 1:

Create a new Image (File->New…)

Width: 12 inches

Height: 12 inches

Resolution: 72 pixels/inch

Mode: RGB Color

Contents: Transparent

Step 2:

Create a new Layer (Layer->New->Layer…)

Name: Primary Blue

Color: Blue

Mode: Screen

Create a new Layer (Layer->New->Layer…)

Name: Primary Red

Color: Red

Mode: Screen

Create a new Layer (Layer->New->Layer…)

Name: Primary Green

Color: Green

Mode: Screen

Step 3:

Select the Elliptical Marquee Tool (M or Shift-M)

While holding SHIFT, click and drag to draw a circle about 3 inches in diameter.

Step 4:

Select the Paint Bucket (G or Shift-G)

Now click on the Foreground Color in the Color Box

Then in the box for Red (R:) put in 255. Make sure Blue and Green are both 0.

Then Press ok.

Now select your PRIMARY RED Layer. Using the Paint Bucket, click inside the circular marquee to fill it with Red.

Click the Foreground Color in the Color Box





Then in the box for Blue (B:) put in 255. Make sure Red and Green are both 0.

Then Press ok.

Now select your PRIMARY BLUE Layer. Using the Paint Bucket, click inside the circular marquee to fill it with Blue.

Click the Foreground Color in the Color Box





Then in the box for Green (B:) put in 255. Make sure Red and Blue are both 0.

Then Press ok.

Now select your PRIMARY GREEN Layer. Using the Paint Bucket, click inside the circular marquee to fill it with Green.

Step 5:

Now arrange the layers with the Move tool (V) so that they overlap creating a white center, and the secondary colors where each two primary circles overlap.

Step 6:

Select the Eyedropper Tool (I)





Click on the yellow area between the red and green circles.

Create a new Layer (Layer->New->Layer…)

Name: Secondary Yellow

Color: Yellow

Mode: Normal

Opacity: 75%

Hold down the SHIFT key and click on a primary color layer. This will create your circular marquee again.

Select the Secondary Yellow Layer.

Select the Paint Bucket Tool (G, Shift-G)





Click the inside of the circular marquee to fill it.

Select the Eyedropper Tool (I)





Click on the magenta area between the red and blue circles.

Create a new Layer (Layer->New->Layer…)

Name: Secondary Magenta

Color: Red

Mode: Normal

Opacity: 75%

Hold down the SHIFT key and click on a primary color layer. This will create your circular marquee again.

Select the Secondary Magenta Layer.

Select the Paint Bucket Tool (G, Shift-G)





Click the inside of the circular marquee to fill it.

Select the Eyedropper Tool (I)





Click on the cyan area between the blue and green circles.

Create a new Layer (Layer->New->Layer…)

Name: Secondary Cyan

Color: Blue

Mode: Normal

Opacity: 75%

Hold down the SHIFT key and click on a primary color layer. This will create your circular marquee again.

Select the Secondary Cyan Layer.

Select the Paint Bucket Tool (G, Shift-G)





Click the inside of the circular marquee to fill it.

Step 7:

Use the Move tool (V) to position the secondary color layers over top of the intersections of the primary colors.





When positioned correctly they will create the Tertiary colors.

Step 8:

You can now flatten the image or save it as is.