Here is a painting by Anders Zorn, showing the narrow range of colors used in the picture. The scheme is centered in yellows and oranges. The "extra-gamut" colors (colors that don't appear in the scheme) are magenta, blue, cyan, and green.
This image has a wider gamut, extending across neutral gray at the center of the circle. It has full intensity yellows and reds as well as some cyan, green, and violet. The gamut doesn't reach all the way to the outer edges of the circle because some hues are only partially saturated.
Here's a fine example of a complementary gamut, a narrow slice of the color wheel from orange to cyan-blue.
The gamut mapping idea is useful both for analyzing color schemes, as we see here, but also for generating the color schemes that you want for your picture.
Further reading and exploration
Christian Romero's KGamut (samples) and free download (It works in Windows with Linux and WINE and it worked fine - openSUSE 12.2. ;-)
There are other digital tools at Live Painting Lessons
There's more about gamut mapping in my book Available on Amazon and signed from my web store.
Previously on GurneyJourney:Gamut Masking, Part 1
Gamut Masking, Part 2