If GS allows change of different dial colours then it would be truly amazing.
Yeah agreed. I haven't heard of any such accounts before either.My understanding is that you can only swap for the dial from the identical complementary post-2017 model (e.g. SBGA011 -> SBGA211). If your watch doesn't have a post-2017 model then no swap.
This would make sense as this is what would be done if your dial were damaged. If you had an SGS SBGA011 that had a damaged dial, they wouldn't have an old SGS dial laying around to put in it, and they'd have to put the newer GS SBGA211 dial in it. It's still the same watch (Snowflake) just with the updated branding.
But doing something like putting the midnight blue dial of an SBGA375 into the champagne-dialed SBGA373 effectively changes the model of the watch. Now the serial number is for an A373, but it has a midnight blue dial. I don't think GS would do that. But I haven't heard of any first hand accounts from anybody who has tried.