Four computers can be found outside the spawn room. They will be flashing the colours, Red, Green, Blue, and Yellow. Interact with the colours as they appear, clicking them on the helper to help you keep track of them.
Tap each colour as it flashes, in the order it flashes, for as long as the sequence runs. The order you tapped is listed underneath. Tap Undo if you mistime one, or Reset to start the sequence again.