Purples are the line meant for 24/7 video recording... Reds are for NAS/Raided configurations...
BTW, to bring up a very recent experience about SATA cables... I recently upgraded my SSD, cloned from one to the other, perfect alignment, but I had some serious performance issues, very slow reads, and very slow writes, almost as if the SSD was a low-end HDD. After trouble-shooting, it was the cable that had gone bad, good enough it worked, but cause some serious issues that you wouldn't think is related to a cable.
But yeah, the PSU does sound old enough that it may not be cutting the power in a clean fashion, power goes out, and the rails just slowly drop down and dont cut off with in a tight enough tolerance.
just a few bucks more than the red, same warranty, but mean specifically for constant read/write.