Buy the instructions for making one of our ever-popular optical illusion afghans.
If you can knit garter stitch, you can make this. It is very easy to knit in seven columns which are then joined together, making it a very portable project. Any yarn can be used. The original was Aran weight. If you use a thinner yarn you may need to add extra rows and/or columns.
I am sure you can see the optical effects so you might like to consider whether you are looking at hexagons or octagons.
The booklet comes with an outline drawing for you to try out your own colour combinations.