Stripped fish ID?

A blue fish with red stribes in need of i.d.

Looks like an Orange lined triggerfish,  Balistapus undulatus

Indeed Balistapus undulatus. One of the more common triggerfish. Several triggerfish have spikes/brushes on their tail base. A little like the lancet of surgeon/unicornfishes. This includes the orangelined triggerfish as shown in the image below.

It is much more extreme in the filefish Amanses scopas (broom filefish) where there is also strong sexual dimorphism with females having a b(r)ush and males long spikes. I'm not sure about sexual dimorphism for the orangelined triggerfish but some have more pronounced spikes. I should check this out better on my next trip. The image below shows a blow-up of a different individual with more prominent spikes.

All my Philippine images have the dark spot on the tail base whereas all my Red Sea images do not. Checking on FishBase they describe it as having the black spot but their image collection supports that it distinguishes Indian Ocean (no spot) from Western Pacific (with spot) populations. I'll check that out in more detail.

Good points and great description!  I will keep it in mind on my next dives, hopefully I can get some clear triggerfish photos, particularly of their nasty tail razors!