Changing colors on Orange Scatterplot widget?
I just realised I'd missed the 'colour' widget. By connecting the data table to the 'colour' widget, I could set what colour I wanted different data sets to be. Then I could attach the colour widget to my scatter plot, and BAM, the colours I wanted. I needed to make sure the scatter plot widget was connected to both the colour widget and the data table. There may be a more streamlined way to do it, but that worked. 

(Posting my own answer rather than deleting, in case anyone else has similar issues).