I have used them, but never measured the color- that is a lot of work. In fact, anyone know of a table of RGB values of FS paints? The paints work and thin just like the MM paints. I assume the difference is the colors.
One thing I like about the little square bottles- if I do not clean the threads well enough when I replace the cap, I can still take the cap off again. I made a fork out of 1/8 inch aluminum and screwed it to my workbench. The opening in the fork is cut to match the width of the bottles. I grab the cap with my pliers and fit the bottle in the fork and then turn. Even with those rubber jar opening sheets I have ruined a few jars of MM by letting the threads get too dirty.