You will need a top color (+- 60m) and bottom color (+- 50m), which can be the same if you want a one-color octopus, and some scraps of white and black (or others) or two safety eyes if you want either version with eyes. I used dark green Royal Shine for the top and white Milan for the bottom but you can use whatever you like.

Finished octopus is almost 30cm from tip of one arm to the other, and 14cm high.