When I create layouts on my Mac using Custom Colors I seem to have complete control. When I enter the same values on Windows, I get totally different colors, and once hue, saturation, and brightness are set it seems to force the RGB values rather than accept my input. The color differences are greater than might be expected just due to different monitors. Anyone have a solution to matching colors across platforms? Is there a basic difference in how color is managed between the two operating systems? Thanks in advance.

Is there a basic difference in how color is managed between the two operating systems?

Yes, there is, but this is hardly a Filemaker-specific issue, and we could discuss it for weeks. To get a little closer to your issue: Filemaker stores its colors as RGB. If you specify your colors in another color space, they need to be converted to RGB before Filemaker can use them. There are many HSB/HSV/HSL models out there, and no single agreed standard. You are much more likely to get similar colors across platforms if you specify the same RGB values.

Thanks for the tip.