Could know that a filter blocks some colours

Should know that a filter lets some colours through

Must know that white light is a mixture of the three primary colours

White light Red light comes through

Red filter

Blue light absorbedGreen light absorbed

White light Green light comes through

Green filter

Blue light absorbedRed light absorbed

White light Blue light comes through

Blue filter

Red light absorbed

Green light absorbed

White light Cyan light comes through

Cyan filter

Red light absorbed

White light Magenta light comes through

Magenta filter

Green light absorbed

White light Yellow light comes through

Yellow filter

Blue light absorbed