The emulator I've been testing with is the 2020/05/17 release of NintendulatorNRS.
I thought it would've been as simple as...
- Writing the correct value ($86) to $2010 to enable 4BPP for BG/Sprites and New Color Mode
- Writing the LSB values of the palette starting at $3F00
- Writing the MSB values of the palette starting at $3F80
I've tested this using an un-headered .bin file (with the CHR data followed by PRG), and a .nes file with the proper(?) NES 2.0 header (mapper 256, submapper 0, flags 7 having "Extended Console Type" set, header byte 0x13 set to 0x07).
Source code and binaries are included in the attached post. Any help (aside from "use the official VRT SDK") would be appreciated.