LyseBlue is a solution that turns blue during alkaline lysis of E.coli and white upon neutralization.

Its color looks like a common pH indicator thymolphthalein and it is definitely thymolphthalein.

Evidence:

-  Thymolphthalein's color transition point is at about pH 9.3. I did crude titration of LyseBlue and blue color appeared at around 9.5.

- Not sure about concentration of the 1000X solution but this post says that it is 43 mg/ml in ethanol. If you have any thymolphthalein lying around in the lab, this would be trivial to test spectrophotometrically against LyseBlue dilution.