I watched it yesterday while doing schoolwork, and it was okay. Watchable, but the movie adaption of Hogfather was much better. The Colour of Magic movie was more absurd, and the casting I thought was very good; Sean Astin (though he kept making me think of Samwise Gamgee) was a fantastic Twoflower, and David Jason was a superb Rincewind. The luggage was a wee bit different than how I pictured it, and played a much less prominent role in the film, which made me sad.
My main objection to the film was its deviations from the book, and what scenes it chose to portray. It left out a good chunk of things; such as flying on a cloud, waiting for rescue in the Kingdom of Krull, the game of the Gods, the Temple of Bel-Shamharoth, and others. They chose to include my least favorite part, the Wyrmberg, which I felt could have been better replaced by Bel-Shamharoth’s Temple. In the end, I was unhappy with the plot changes the film-makers chose to make, and think they should have chosen something else to adapt, as opposed to trying to squeeze those two books into one movie. Doubtless for one who hadn’t read the books, the movie would have been good, though.
The other major objection I had was that the inter-wizard rivalry was given much more attention in the movie. And I don’t like Tim Curry as an actor, so having him play Trymon made me unhappy; he came across as actively malicious and evil in the movie, but in the books he’s just an OCD maniac. Also, on a parting note, Trymon in the movie looks a lot like a much older and angrier version of Joacim Cans (lead singer of the band HammerFall):
So, in summary, watch it if you haven’t read the books. If you have, it might be best to steer clear and watch Hogfather instead.