Monitor color check
Look at the image.
1. There are 21 steps from left to right.
2. The colors from top to bottom are 12, these are 30 degrees apart in the color wheel.
If you're monitor is good and calibrated you should see 21 distinct steps for every color.
Same as above
But look at the 2-3 brightest steps (from the left) are they any different? If not, something is wrong!