Can't set colors for ofxGui

I can set the font in ‘setup’ for a panel like this:

ofxGuiSetFont("/Users/fred/fonts/FreeSansBold.ttf", 18);

But I can’t set any colors for text, header background of panel etc. - this does nothing:

    ofColor green (50,200,50);
    ofxGuiSetTextColor(green);

What am I missing?
I’m on OSX Big Sur, OF 0.11.2

TIA

try to call the above customizations before gui.setup()