Blue is alkaline (low) and yellow is acidic (high)
Color should be green for good ph (mid range)

http://www.thetropicaltank.co.uk/Images/phdiag.gif

On a high range test kit,yellow is low @ 6.0 and blue is high @ 8.0. Some test as low as 5.0, whatever color they use the number tells you if its high or low.

Hope this helps.