This displays the regular palette on the top, and lets you play with emphasis/greyscale bits for the palette on the bottom. You can also toggle the "forbidden black" $0D color.
I tested it on a bunch of different emulators, and on my NTSC NES. It should presumably work with Dendy. The PAL version of the ROM has only been tested in emulators.
Further down in this thread, there are two other useful programs:
- color_test.nes - a simpler full-screen colour test
- capture_nes_palette.py - a script for compiling palettes from test captures