This routine updates the VNT3+1 location in the IRQ1 handler to change the
palette that's applied to the top part of the screen (the four-colour mode 1
part). The parameter is the offset within the TVT3 palette block of the
desired palette.
Arguments:AThe offset within the TVT3 table of palettes: * 0 = Yellow, red, cyan palette (space view) * 16 = Yellow, red, white palette (charts) * 32 = Yellow, white, cyan palette (title screen) * 48 = Yellow, magenta, white palette (trading)
.DOVDU19STAVNT3+1\ Store the new colour in VNT3+1, in the IRQ1 routine,\ which modifies which TVT3 palette block gets applied\ to the mode 1 part of the screenRTS\ Return from the subroutine