If it is busted lower down... you can straighten and splint it...
However... if the color of the leg has changed, then the circulation has been compromised. ..probably the lower part will die, rot and fall off. With the Risk Of Causing infection...
Here are a few links that might help.
If you splint, it's important that you watch for swelling. Wrap tight enough to do the job, but not too tight. It can take several weeks for healing enough that the bone has start to knit, and a month or more for complete healing. Lower leg breaks have the best chance of healing. Upper leg, near the hip, are much more problematic and can require pinning (avian vet surgery) to enable healing. Best of luck.