Kurenai is a weird case. The "first" solo, played by Tomo and/or Eddie was one. Then Jun played different, then hide played different and changed again during Dahlia Tour. Then now with Sugizo, they got back to the "first hide version".
I think is very possible that it was composed by Taiji, as once I found (don't remember where) a 1986 recording of Kurenai, which sounded like it has only one guitar, and was pretty much like the one we know.
We know that hide was a huge influence on composing of X. I think the main solos was composed by both him and Taiji, as Yoshiki seems to be like HURR DURR HOW DO I PLAY GUITUR, as we can see in the new songs, which are 100% written by him. I.V. doesn't have a guitar solo, only a noisy part where Sugizo do some improvisation with whammy bar, and Jade and BTBF have pretty lame solos. Scarlet Love Song doesn't have either.