"Hispanic" is a linguistic classification (anyone whose ancestry is from a Spanish-speaking country is Hispanic) and not a racial one, though most media talking heads and DWFs treat "Hispanic" as a race, typically out of ignorance (for the DWFs) or for their own political agenda (for the media). There are white Hispanics, brown Hispanics, and black Hispanics. A snow-white Spaniard and a black Dominican are both classified as "Hispanic" though they obviously have nothing in common racially.
As for white Hispanics vs. non-white Hispanics, it's not so much skin tone as it is basic common sense. Anyone with eyes can simply look at Zane Gonzalez and tell that he's a white man. And they can do the same with Ryan Santoso and tell that he's not.
Another good way to tell is that white Hispanic NFL players are discriminated against and bashed by the media like any other white player, while non-white Hispanics are praised. Zane Gonzalez is considered "just another unathletic white kicker," Blake Martinez never gets credit for being a great linebacker, Tony Romo was labeled a "choker," etc. On the other side, non-white Mark Sanchez had excuse after excuse made for him by the media (until he buttfumbled and even they couldn't cover for him anymore), Aaron Hernandez was praised as a "diverse" hero (until he committed murder, then he mysteriously became white). Etc.