Where does xterm get its colours on KDE, if it the colours are not passed as an option?

Note that my ~/.Xdefaults doesn't contain any reference to Xterm. The only settings in .Xdefaults related to colours are:

OpenWindows.WorkspaceColor: #a6d0fa
OpenWindows.WindowColor: #cccccc

I normally do not use xterm (preferring kterm instead), but I'm using an application which starts one, and I would like to change its foreground and background colours (because they are nearly the same, making the text hard to read). I know that the application just starts "xterm" without parameters, so this must be the default colours xterm gets from somewhere (and indeed, if I invoke xterm manually, I get the same colours).

I checked Configure KDE Control Center / Appearance / Colours, but the settings for StandardBackground and StandardText are NOT the colours I can see in xterm, so xterm must take them from a different location.