Hey Alex,
Yes, you are correct about the red heat shield. When Bandai first issued the 1/55 VF-1S Strike Valkyrie, it came with a screw-in "amber canopy" and a screw-in "black canopy" which could be interchanged; but not with out unscrewing it. As far as I know there was no painted skull on either colored heatshield; the skull sticker had to be added to achieve the full look. Perhaps it didn't dawn on Bandai during the Strike Valk's production run until later, that the Hikaru Strike should have a red heat shield; instead of black.
This error was later corrected via an in-store promotion, where a Strike owner feeling the need to be complete with a red heat shield, could pluck an order form off a POP (point of purchase) display and get a clip-on heat shield directly from Bandai. Along with the order form, Bandai also gave you a free "Hi-Metal" sticker that was available from the POP display. The actual display included several order forms & Hi-Metal stickers; along with a few red clip-on heat shields for show only. This same clip-on red heat shield was later inlcuded in the 1/55 Bandai Hikaru VF-1A.
Hope this helps...