János, It's too late to warn me. Yet another victim in the "watch out calibrating Dell U2410 in the Custom Colors mode" story :))) As I said initially I tried to understand how much colors my display is capable of, I tried to estimate it's native gamut. And that's why I was concerned about Custom Colors settings. My today's experiment confirms most of your statements. Using the Graeme's advices I was able to setup properly RGBCMY Hue. But oh my God what it lead to. Immediately before calibration I noted various kinds of color defects on the black to primaries gradients, clippings, tinting, etc. E.g. magenta looked real magenta when its saturation was 100, but at this value about a third part of black to magenta stepped gradient at the lights looked solid, and the middle steps were pink. Black to yellow and black to cyan gradients were green tinted in the middle. Black to RGB were fine, though I had to desaturate R and B to some extent. Despite all visible color defects I continued with calibration and profiling. Just if someone is interesting the color profile is in attachment. Native gamut is almost everywhere beats AdobeRGB. But of course calibration didn't fixed all color defects. Right vertical bar of this test image ( http://www.realcolor.ru/assets/images/monitortest/RealColor.ru_MonitorTest_1920x1200.png) looked terribly. Also magenta clipping and tinting are not disappeared and also clippings/bandings on some kinds of smooth color gradients were visible. So, my conclusion is that Dell U2410's is physically capable of beautiful colors, where as its hardware and/or firmware are/is not. And it seems I will stick to Standard also. It's a pity, I liked bright saturated colors of the "Custom Colors" preset. :)) Best regards, Ivan