Yellow
From Enwikikids
Yellow is the color of:
Yellow can represent light and the sun's rays. It can also be a sign of cowardice.
On road signs, yellow means "warning" or "danger". It is used to mean this because it is easy to see. Some animals, like bees and hornets, also use the color as a warning so that other animals will know to stay away from them.
Inkjet printers use yellow ink as one of their three basic colors, along with cyan ink and magenta ink.