It was the first programmable electronic digital computing machine, yes. Special-purpose computing machines had been around since the 1600's (where they were used as textile weaving machines I think).

And the “electronic” part is important. The Z3 predates in by 2 years and was a programmable digital computer, except it used electromechanical relays.

The Z3 is arguably more programmable than colossus and it was proven to be Turing complete in its stock configuration. Though the Z3 lacked the ability to conditionally branch, so nobody realised it at the time.