My only reference lists either blue finish or nickle.
Normally, a factory-applied blue finish would be blue, like your gun's barrel and cylinder.
Normally, a purple finish indicates a blue job done at an incorrect temperature, which might be un-factory-like, even for a cheap gun like an IJ.
Further evidence is to be found in your picture of its caliber marking on its frame.
The stamped letters and numbers are partly polished out and indistinct, indicating a poorly-done, amateur's polish job.
Also, the frame's edges and corners appear somewhat rounded. Usually, this, too, means an inexperienced-amateur's polishing job.
I think that there's been an amateur's refinishing job, but only on the frame. The cylinder's edges seem sharp.
However, the purple color seems very uniform. This indicates to me that it may have been made purple on purpose.
Normally, a botched blue job will be blotchy, not uniform in color.
So, I vote for an amateur's refinishing job on only the frame, with the re-bluing done at the wrong temperature on purpose, in order to achieve the purple color.
However, it is possible that your pistol was made by IJ at a time when they were going through the financial difficulties which eventually killed the brand, so that the polishing and bluing work done on your pistol was a little haphazard and slapdash, done by relatively inexperienced workers.
You might check its serial number against production records, to find out when it had been made versus when IJ went out of business for the first time. That might help.