Hey Lapis, well you got me thinking and here's another way...

Basically do the same as before up to the Stroke step
but this time choose Gradient from the "fill type" setting.

Now choose a gradient colour set, (i used the default Black and White) To call up the gradient settings, click on the colour bar.

Now click on the black colour stop in the bottom left corner of the gradient preview.

Move your cursor to the "Location" textbox and enter 50% and do the same to the white. Click OKAY to get back to the Stroke settings.

Play around with settings to see what different effects you can achieve. Just make sure you select REVERSE to swap the colours.

just another way to get the same results,

:)
retrocity