I haven't tried this, so don't know if it works but you should be able to use a series of commands:

RANDOM - to generate a random number (multiply the result of the command by 360 to get random degrees)

SHADEPOLY - to make it a shaded polygon at the randomized angle

SETFSFLAGS 192 - Turns off shading by light, leaving only rotation.

Good work.

CHANGEC requires a color number (black is 0), so unless you have defined a variable called BLACK and set it to 0, that's why it fails for you.

Note that even if you do not know the name of the fill, you can still use CHANGEFS, if you just let the fill name be blank when asked and just hit enter, you will get the fill style dialog where you can pick your fill. (But admittedly, picking through MPEDIT is probably easier as it is a single dropdown, not a dialog with 4 pages)

If you know the name of the fill to change to, the quickest is to use the CHANGEFS command. Type in the command (followed by enter), pick the poly when CC3+ asks for selection, hit D for Do it, and when it asks for the new fill, type in solid white 20 and hit enter. Changing it via the command line do require that you spell the new fill 100% correct though.

Of course, you can also use the more common GUI dialog through :CC2MCHANGE:. If you wish the correct fill style to be pre-filled in this dialog, first use the KEEP (:CC2KEEP:) command on another entity that has the correct fill, and when you then use change properties on the entity you want to change, the fill style you extracted from the other entity is already pre-filled, all you have to do is to check the check box in front to apply it.

If you look at the fills for your polys, you'll notice that all of them (except "F") are filled with "Solid white 20". This is a partially transparent fill, that lets the background shine through.

"F" on the other hand is filled with a plain solid fill, set to white. This isn't transparent at all, and leads to the white appearance. This doesn't have anything to do with the effects at all. Change the fill to solid white 20, and you should see it appear as the rest of them.

On an unrelated note, I also noticed that while you do have a separate sheet for each of the polys, poly "F" is on the contour 4 sheet, NOT the sheet dedicated to it.