gtk:widget-override-symbolic-color (widget name color)

widget -- a gtk:widget object
name -- a string with the name of the symbolic color to modify
color -- a gdk:rgba color to assign, or nil to undo the effect of previous calls

Sets a symbolic color for a widget. All other style values are left untouched. See the gtk:widget-override-color for overriding the foreground or background color. The gtk:widget-override-symbolic-color function has been deprecated since version 3.16 and should not be used in newly written code. This function is not useful in the context of CSS-based rendering. If you wish to change the color used to render symbolic icons you should use a custom CSS style, through an application specific gtk:style-provider object and a CSS style class.