Editing icons for factions

[Zxy44]

Is anyone here familiar with adding new icons for factions on the world map.
I create them in PS in RGB mode and save them as .png
Unfortunately on the map it creates a strange color border which spoils the whole effect. Does anyone have any idea or experience how to get rid of this?

[Zxy44]

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[Zxy44]

this is what it looks like in PS