This design is essentially a modular construction, but using a self-striping yarn will go some way to disguise the precise nature of construction. In the red/white/blue colour way that I used, the finished socks look very much like somebody took the British Union Jack, smashed it into little pieces and re-assembled the pieces into a sock shape, hence the name. Other colour choices will of course produce a completely different effect. - General Hogbuffer

Errata:
The instructions for the second row of the B triangle should read:

Row 2 (RS): K4, wrap next st, turn

There is no wrap on the 3rd st, so no need to hide it.

25/04/2020: I have just added a free link to the pattern, but please be aware that this is my original pattern before tech editing and may contain errors.