ini directives on the command line

I want to override the “stdcolors” directive in my ini file and use the command line option

//stdcolors=

but the syntax for that directive is “color on color” and when using the command line option space are not permitted, I would like to set it as if was not set in the ini file at all. I tried stdcolors=default but that did not work. Is “stdcolors” one of the directives that is not setable on the command line?