The important part is where it specifically says Ads, and then a link to why these ads? though. Contrast should be high enough you can see why ads end, but other than where it's been cropped in the picture you posted, it's still very clear that at least the top result is an advert. You are right that contrast should clearly distinguish ads from not, but you shouldn't crop out the label clearly identifying it as an advert to prove your point.

In addition to that, I'd argue looking at your picture that it really doesn't matter if it's an ad or not - if it were an organic result and you didn't want to file a lawsuit, you wouldn't click it anyway.