Why do certain style changes not show up on the canvas?

When you are making changes in the style editor and these changes do not seem to appear on the canvas, this is most likely due to a screen-width specific style overriding the style you have just changed. Make sure you are in EXPERT mode, and use the screen-width selectors at the top of the style editor to check if there a responsive style overriding the style you're trying to set. For more information about responsive design and mobile first design, please have a look here.