I respectfully disagree. It depends on the stone. If the blue green color has significant grey tones, rose or yellow gokd bring out more blue. White metal can make the stone appea more grayish. If the stone has great saturation of color, any metal would do. The OP’s stone, imho, would look best in yellow gold, but that’s after I set similar colored gems in yellow.White gold is the best for a blue-green colour, it makes it pop so much!