--------V-10101B----------------------------- INT 10 - VIDEO - PERFORM GRAY-SCALE SUMMING (VGA/MCGA) AX = 101Bh BX = starting […]
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--------V-10101B-----------------------------
INT 10 - VIDEO - PERFORM GRAY-SCALE SUMMING (VGA/MCGA)
AX = 101Bh
BX = starting palette register
CX = number of registers to convert
Return: nothing
Desc: convert the RGB values of one or more palette registers such that the
resulting values are grays with the same intensities as the original
colors
SeeAlso: AH=12h/BL=33h

--------V-1012--BL33------------------------- INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA, MCGA) - GRAY-SCALE SUMMING AH = […]
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--------V-1012--BL33-------------------------
INT 10 - VIDEO - ALTERNATE FUNCTION SELECT (VGA, MCGA) - GRAY-SCALE SUMMING
AH = 12h
BL = 33h
AL = new state
00h enable gray scale summing
01h disable gray scale summing
Return: AL = 12h if function supported
Desc: specify whether or not colors should be converted to gray scale when
palette or color registers are loaded
SeeAlso: AX=101Bh,AX=BF06h,AX=BF08h

I think I made a tiny assembler COM file for doing this. Just run it before any other program.

Yes, I so too did, but it it is necessary to put the adapter, at least VGA. I still directly changed registers DAC to make shades of the green.

maybe buy a colour monitor if you have cga card.

CGA monochrome supports higher resolution than color mode. (640x200) And with tweaking in composite mode, can be both high-resolution and high-color. (Relatively speaking, of course.)

Plus, the OP is referring to support in DOSBox.

(I used to have an HP 200LX, which has a "CGA monochrome" display. I found Windows 3.0 CGA drivers to run on it, so I could play my Windows Solitaire.)

I guess you'll find other ways to play solitaire.

but dosbox supports 640x200 in composite mode so it should be possible in dosbox too 😀

we don't add stuff, just because it is possible.

I just wanted to say that it is possible in dosbox right now without any stuff added, as what Anonymous Freak said looks like he doesn't know about it. 😀

Having once owned a monochrome CGA monitor in the 80s, the green would be a brighter and appropriately go with flicker and VERY VISIBLE scanlines

iirc, yhkwong's build can simulate what you want by using some shader that does the screen in with green and has ghosting to go with it, too

Very visible scanlines on monochrome CGA monitor, and also on EGA monitor in modes with 200 lines look very bewitching. It is romanticism of old monitors.
By the way, some emulators of slot machines emulate well visible scanlines. Simply between lines the interval becomes.