First, the Taylor TA test turns from green to red. If it is turning purple then you have a biguanide (SoftSwim, Baquacil) pool!
The color change on the CH test is from a pink to a sky blue. This document from the Taylor website illustrates this color chagne and info on the color changes of the TA test
http://www.taylortechnologies.com/Ch...P?ContentID=35

If you are having trouble seeing the color change then add a few more drops of the indicator solution to your sample or try using a 10 ml sample where each drop is 25 ppm CH. TO do so you would add 10 drops of calcium buffer to the 10 ml sample, 3 drops of indicator, and then titrate.
If your color changes to a blue color that reverts to purple (fanding endpoint) you probably have metals in the water (a common interference). If the color has changed from pink to purple then you have not finsihed the titiration and reached the blue endpoint. Remember, if you have high calcium hardness and are using a 25 ml sample size it can take 20, 30, 40, 50, 60, or even more drops of titrant to see the color change to a blue.

The Alex system is designed to maximize chemical sales for your Bioguard dealer and is not to be trusted. IT also uses a strip reader so it cannot give you a calcium hardness reading, only a total hardness reading.

The calcium hardness titration of calcon indicator or one of the eriochrome indicators with EDTA in an akaline solution to remove the magnesium hardness is the standard test for calcium hardness and is the one Taylor uses.