Ah! I see what you mean. When the following conditions are met:

Style = 2
DisabledBackColor = RGB(255,255,255)
DisabledForeColor = RGB(0,0,0)

then VFP will "grey out" the text by dithering it. In the case that the properties are not these exact values, then the behavior is according to the DisabledBackCOlor and DisabledForeColor properties. In the online help for the DisabledBackColor and DisabledForeColor properties, there is a remark stating that "The color you specify is dithered with gray" -- which is not entirely true, as this only happens in the given case.