annotate with two different colors based on threshold

I added the capability to annotate an image with features of two different colors. I found this useful for playing around with cutoff thresholds. e.g. see how many features you miss if you increase the minimum size.
I think that the code, as written, will *never* put anything into a list, scalar or not. A multi-element tuple always evaluates to True.

I can say that I definitely get the wrong behavior when I try this code at the IPython prompt.