Yes there are more colors. Clicking the color-select box for Fill or Line displays a palette with 88 colors and an "Other Color..." option. Selecting Other Color allows you to enter RGB values. You also have the ability to save 16 Custom colors :)
Which version are you using now?
I'm using FMP 10, but I have just discovered that the problem is most likely with the color picker's magnifying glass function.
Let's say I'm setting the background color of the header. If I bring up the color picker by selecting "Other Color..." at the bottom of the color palette, then click the magnifying glass, then click on the color I'm after, the correct RGB numbers, 0,75,59, get entered into the little boxes in the color picker. By "correct", I mean matching the DigitalColor Meter's numbers. If I then click on the OK button in the color picker, the header color becomes 27,74,59. This sort of behavior is typical of a color system using a limited color palette.
Now that I have been using the color picker's magnifying glass elsewhere (to add more background area to the logo image, for exaple), I see that this happens with Graphic Converter and other apps as well. I discovered that if you use the magnifying glass to pick up the color numbers, then close the color picker, then open it again and type in those same numbers, the color of the background is set correctly. So, problem worked around.
Oddly, if I use the magnifying glass to pick the color, then drag it down to the palette for later use, it shows the correct RGB values when you click on it, but transfers the wrong ones. I suspect it has something to do with the dogear that appears on the tiny color sample in the palette. If there is no dogear, for example with colors set by typing in the RGB number or sliding the sliders, then the color is set to match the numbers. This makes this look like a feature instead of a bug, but I have no idea where to find the meaning of the dogear or how to make the color picker behave in a manner that (to me) makes sense. Does anybody know what is going on with the color picker?
Thanks for your help, folks.