Adobe Premiere: PNG transparency ist not interpreted correctly
I don't have the files to look at, so I can't say for sure, but if you're importing a flat PNG Premiere should interpret the transparency correctly and convert it with transparency on the alpha layer. 

One thought, make sure you're using layer the PNG on layer 2 or above. 

Second, make sure you are placing the PNG above a filled video layer (Black Video), File -> New -> Black Video

Third, if that still gives you problems, try saving your file as a layered PSD file in Photoshop. Import it in and when prompted/select the import the layers as individual layers. 

Then place the layers as needed and in what order on your timeline. 

Lastly, it could possibly be your timeline/sequence settings - importing in a 24 bit PNG to a lower bit depth sequence could and would cause color issues if the sequence doesnt support that bit depth. 

Last, you should be working in sRGB unless there's a specific need for another workspace.

Hope this helps.