Muriatic acid (hydrochloric acid) is colorless. The only common inorganic
acid I can think of with much color to it is oleum (sulfuric acid with
extra sulfur trioxide), which is somewhat yellow. I hope nobody on this
list sees any, though, as it is quite dangerous stuff. Probably (more or
less certainly if it is a solid and not a liquid) the Seachem product is a
weak acid, and not one of the strong inorganics.
There is one common thread I have seen in a few recent messages here and in
*.aquaria; a horror of "chemical soup." Ummmm... what's that when it's at
home? You can in fact have a nice stable water chemistry with several
buffer systems running at once. You can even calculate pretty easily what
the acid titration curve would look like with your favorite mix. So why
the horror of having more than pure carbonate chemistry affecting pH? What
strange soups are people creating?
A bit of trivia for buffer loonies: your blood combines carbonate and
phosphate buffering systems (actively regulated, at least while you are
martin-h at mail_utexas.edu