I took a quick look - initially I was thinking they'd be doing something smart, like using CSS blending filters or a text-mask technique as to avoid duplicating HTML markup - but alas, no: duplicating HTM is exactly what they're doing: there's two copies of the sidebar HTML (`div.gta-article--scroller--top` and `div.gta-article--scroller--bottom`), the one with white-text is z-ordered above the scrolling gradient, the other (with green text) is z-ordered behind it.
I'm surprised at the extent people still compromise their HTML for CSS effects when it really isn't necessary - the curse of divitis still exists :/