Hmm...
I worked on 8 Color CRT's (they were a significant upgrade from my first
several computers), but not willing to trust my memory, I checked XL's
self-documentation...
In both the XL03 and the MacXL color palette tooltips, the color
corresponding to colorindex 4 is listed as "Bright Green". The "Green"
entry is colorindex 10. That applies to both Font and Background color.
OTOH Green corresponding to colorindex 4 is in custom number formatting,
e.g., [GREEN]0.00;[RED]0.00;[YELLOW]0.00;@
XL/VBA Help (and the vbGreen enumerated constant) say Green = RGB(0,
255, 0). RGB(0, 255, 0) = 65280. However, after setting
ActiveCell.Font.Color = RGB(0, 255, 0), I get
?activecell.font.color
1357599
which corresponds to rgb(31,183,20).
(And of course, for the VBA QBColor function Green = 2...)
So once again, MS has created a slew of internal inconsistencies.
Since the OP didn't distinguish between font and background color, much
less between color and colorindex, I don't have a clue which one is
appropriate.