Nice!! Got 4, but I am a gun paint tinter.

worked in a paint shop for 2 years.
I find this test somewhat mis-leading, it is similar to a common trick I like to pull on customers. It is not so much a deficiancy of colour definition, rather an optical illusion.
When you put colour in a gradient situation like that and ask someone to sort them, it is more a puzzle than a deficiancy test. You will find the more you sort / switch the hues the closer you will come.
Try the test again, pick up squares and note the hue, move it along quckly to a new spot. If you can recall through memory the square may "appear" a completly different colour to when it was positioned between two other hues.
It is you brain analysing the grouping of hues, not just the individual hue selected.
So if you are scanning the line, it may indeed look right, yet is not due to this.
Take a look at the brown tile in the center of the top face and the yellow tile in the center of the side facing slightly to the left. They're the same color.
See what I mean? colours are manipulated by those around it. This is not a deficiancy, it's a optical illusion.
The test is reasonably accurate, but thought I would let you know there is more to it.
In the paint shop, I like to illustrate this to customers by shifting a colour chip in between different colours. No wonder customers complain their paint doesn't look as they expected. They will swear the two chips of the same colour are different, they are not, just the coulours around them manipulate their colour in your brain.
Paint companies are also aware of this phenominum and use it to their advantage in their colour brosures.
If you don't believe me about the cube, take the pic and edit it, take the dropper, and select the brown tile then the "yellow" tile they are the same colour.
The image used is Copyright of R.Beau Lotto and is not to be used for profitable purposes only educational.