I actually have no idea now. Whenever I was trying to fix it, the material I made for the stripe updated to whatever the black material was even though I didn't press anything other than selecting the original material in the list. A mystery! I just re-assigned it the same material as the base of the launchpad to feign the color.
It might be because I accidentally applied the glowing effect to the stripe instead of to the placeholder particle for the smoke, but I thought I had returned it to how it was before I made that mistake. Apparently not!
That could be! If you don't figure it out, feel free to upload the file to pasteall.org or something and share it here.