Primary and Secondary Colors

An image showing the three primary colors: Red, Green and Blue and then the three secondary colors: Magenta(right), Cyan(left) and Yellow. The mix of all 3 is White.

Here is a sample question associated with colors, typical of lower secondary……

Question: State the colour of the objects when they are placed in different colours of light.
Colour in White light/ Colour in cyan light/ Colour in red light
d)White /


Colour in White light/ Colour in cyan light/ Colour in red light
a)Green / Green / Black
b)Yellow / Green / Red
c)Magenta / Blue / Red
d)White / Cyan / Red
e)Blue ……

There are 3 primary colors: Red, Green and Blue. The secondary colors contain two of the three primaries:

Yellow contains Red and Green
Cyan contains Green and Blue
Magenta contains Red and Blue.

White light contains all 3 primary colors.

a)So if something is green in white light then it reflects only one of the primary colors. Cyan contains green and blue – the green is reflected and the blue is not. Under red light the green object will look black, since no light is reflected. There is no green within red.

b)If something is yellow in white light, that means it reflects red and green but not blue. Cyan contains green and blue. So it will reflect only the green. Under red light it looks red since yellow reflects red. There is no green for it to reflect under red light, so it does not look yellow anymore.

c)If something is Magenta in white light that means it reflects red and blue but not green. Under Cyan light it will reflect only the blue and under red light it will reflect the red.

d)If something is white under white light it reflects everything, so whatever comes in, gets reflected.

I’ll let the reader do the last one……

Just remember that if a primary color shines on something or a primary is reflected, then there is only one color within that primary. If a secondary color shines on something, there are 2 colors within the secondary.

I have a nice animation that I do in class to show all the colors on a big screen. The funny part about this subject is that many of the assessment books are printed in black and white – it’s much clearer when you can actually see the colors!

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