The medium is YPAD, and it is probably contaminated with bacteria. I suppose this kind must synthesize some pH sensitive molecules as It is reacting with bleach but I can't find any information on this phenomena.
Recall that bleach (NaCLO4) is both a reasonably strong base and a good oxidant.
Do know what the components of "YPAD" are but perhaps there are pH indicators in the media that are effected via the basic nature of bleach or other compounds that are readily oxidized under the basic conditions to red chromophores?
I know some medium have pH indicator but not this one. Moreover, only my contaminated tubes turned red, not the normal cultures. So the medium is certainly not responsible for this.
Try isolating the bacteria. Please post pictures. Does it turn red if you use NaOH, or is it specifically bleach? Can you purify the red compound? Try paper chromatography. Can you extract it?
Sorry, I am late, I didn't see your response. Sadly I discarded the bacteria as it was contamination ( not to mention that there was bleach inside the culture... ). If I ever find it again I will try to isolate the strain and run some test on it.