rim around skyline

As others have mentioned, that is cromatic aberration. The white that you get after you correct the aberration could be haloing from something else you might have done like clarity. Does the haloing occur when you only correct for aberration? 

the green or purple colours often formed against a skyline

By @robyn_0487

This is chromatic aberration, a lens optical flaw.

If this is a raw file, ACR (the Camera Raw processor) has tools to address this. There are two types of chromatic aberration: lateral and axial. The first checkbox is for lateral CA, which is easy to correct. The second set of controls is for axial CA which is a bit more tricky:

Could you please post screenshots taken at View > 100% with the pertinent Panels (Toolbar, Layers, Options Bar, …) visible? 

If a Layer Mask results in noticable edges one may need to edit the Mask (contracting etc.) and/or decontaminate the image’s edges themselves. irrelevant

Unfortunately you haven't given us detailed infos about your issue (like a screenshot) and any information about your system. Therefore, all proposed solutions are a look into the crystal ball.

But I think if you spoke about "the green or purple colours often formed against a skyline" you're talking about chromatic aberration. This can be removed in Camera RAW at it's best. 

See here: 

https://www.youtube.com/watch?v=KPqdBP0jBv0

https://helpx.adobe.com/camera-raw/using/correct-lens-distortions-camera-raw.html

If this doesn't help or it's another issue please give us more details, like screenshot that shows us the issue and the steps you've tried to correct this.