Each QwtText object can have its individual color - if no color has been explicitely assigned the color is usually somehow taken from the widget palette where the QwtText object belongs to.

In case of the title of a QwtScaleWidget it is scaleWidget->palette().color( QPalette::Text ). The tick labels are also painted with QPalette::Text, while ticks and the backbone of the axis are painted with QPalette::WindowText.

Because of Qt3 compatibility Qwt 5.x uses the old names for these roles - check the code.

Uwe

PS: Note, that Qwt is open source. It is allowed to look into the code.