My thoughts as well. Anime only watcher, so I'm completely spitballing theories and observations here.

I just rewatched the entire series yesterday and that was my thought as well. With both Annie and Eren, their eyes and hair color are the same in both human and Titan form. The hair style is a bit different for Eren; it seems to be longer. For Annie, I'm not sure as I can't recall ever seeing her with her hair down.

The lighting's quite dramatic and it has a grey tone to its entire body, but the Armored Titan's hair and eye color does seem to be in the blonde range. What's more telling for me now after episode 29 is the body structure; Armored's body is stocky as fuck and looks strong. So does Reiner, and he was hanging out with Annie during the Battle of Trost. IIRC, neither of them displayed a very openly excited reaction to Eren's transformation.

The Colossal Titan has no skin or hair, so there's no clues about it, only that its second appearance confirmed that it was a Titan shifter as it had no foot steps leading to or away from where it was, and another character says that it likely had Maneuver Gear. Beast Titan's unlike anything we've seen so far; I'm not even convinced yet that he's a Titan shifter, rather, something else.

Shit's fishy as fuck.