Thanks for posting this! Would love to know how this was done. Would be very helpful to be able to spec distinct colors to highlight the Section titles.

Actually just figured this out ​@James_Lawrie:
In the example above, the Section fill color is set to FF00D0 , with an opacity of 1%.However that transparency only applies to the Section background, and not the Section label.

So the result is:
Section label is FF00D0 at 100%
Section background is FF00D0 at 1%  (barely saturated)

I mocked up an example illustrating this below. Pretty cool hack to distinguish the label color from the background color (at least if you are not too concerned with the actual background fill of the section).