I don't think Rowling ever gave that potion a name- in fact, the quote you gave above was the only mention of it in the series.
Here's a little something JK Rowling had to say about it (originally posted on her website, reposted at the MuggleNet.com forums):
JKRowling's website, F.A.Q.
As a vast number of people have pointed out
to me in the last twenty four hours (some of them related to me by
ties of blood) Colin DID develop a photograph from his camera in
'Chamber of Secrets' (my previous answer stated that he never did so).
Cameras, like radios (or, as the wizards call them 'wirelesses' –
they're always a bit behind the times when it comes to Muggle
technology) do exist in the wizarding world (there's a radio in the
Weasleys' kitchen and we know there are cameras because of the moving
photographs you see everywhere). Wizards do not need electricity to
make these things work; they function by magic, but in the case of
such objects the wizards liked the Muggle invention enough to
appropriate the idea without adding cumbersome plugs/batteries.
I have an old notebook in which it says dev sol (potion) magic
[indecipherable word] photos move. Adept as I am at interpreting my
old scribbles, I can tell you that the original idea was that wizards
would use a magical developing potion to make their photographs move.
SO... as Colin's batteries can't work in Hogwarts, clearly his camera
is running off the magical atmosphere and he is then developing his
photographs in the magical potion that causes the figures therein to
move. All of which goes to show that Colin has a lot more initiative
than I ever realised.
dev sol seems to be shorthand for developing solution.