It is Christmas Eve and Tomos is really excited.
His family has a tradition of opening one present before going to bed.
There are several presents under the tree, and Tomos knows he's allowed to open the one wrapped in yellow paper tonight.
Unfortunately, there is a power cut just before retrieving the presents from under the tree.
Thankfully they have some battery powered lights on the Christmas Tree.
The problem is that the lights only have three colour settings: red, green and blue.
Can you identify the yellow present?
Hint: We have an online workshop called Science of Colour which may be of assistance in this challenge.