I used the generic Apple logo and grey text against a white background which is how apple has it on their website. My sketch plugin tells me that it is failed the compliance and that the contrast ratio is 2.3:1 as against the minimum 3.5:1
I'd be very interested in what sketch plugin you're using! I'm about to start a very accessibility-driven project! :)
It might be this Sketch plugin: https://github.com/getflourish/Sketch-Color-Contrast-Analyser
Also it's not a Sketch plugin, but this is a great tool for accessibility: http://wave.webaim.org/
Sorry for the late reply but Brent is right, that's the same plugin I use.