I have found a method that helps distinguish the colors for C or Ph. Take piece of card stock about 3" x4". Cut a slot in one end that is the width of the color bands and long enough to expose the test solution and the color bands. Then hold the card against the test container and move the slot up and down to only view one color at at time to get a match. The eye is very good at side by side comparisons, but when you see all at one time the brain wants to average them out.
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