What is a Cubic Graph? A graph where every node has exactly 3 connecting lines. What is a Proper 3-Edge Colouring? Colouring the lines with 3 colours (Red, Green, Blue) so that no two lines of the same colour touch the same node. Task: Click edges to colour them. Use "Validate Colouring" to check your work. Once validated, use the Remove buttons to hide one colour. Synchronized 3D and 2D views update automatically.