Running

plot(range(10), color='red')

and then opening up the qt4 figure editor, clicking on the curves tab reveals that the color isn't correctly captured by the editor (defaults to black). Making other changes in the editor, unrelated to color (say changing the scale), and then hitting Apply unexpectedly changes the color of the plot. Same thing happens for an alternative like

plot(range(10), color='#ff0000')

Only

plot(range(10), 'r')

interacts correctly with the qt4 figure editor. I'll submit a PR for this.