Translation:Zsuzsa is walking on the yellow bridge.
I'd say pretty much like the difference between "lemon yellow" and "yellow" in English. "Yellow" is the general term, and "lemon yellow" is a more specific shade or hue of it. Sárga is the normal, broad term for yellow, and for an English->Hungarian translation, choosing citromsárga for "yellow" would be oddly overspecific.
In Hungarian, both yellow ("citromsárga") and orange "narancssárga") are types of "sárga", among other shades. But "sárga" by default means "citromsárga". It is just unnecessary most of the time to say "citrom". "Sárga" is sufficient, but there is nothing wrong with using "citromsárga".
In Hungarian, when you say "sárga", you usually mean "citromsárga", that specific shade of bright yellow. It is not usually specified, it is implied. Various shades are specified only when necessary, as in "Nekem ez a (citrom)sárga szoknya jobban tetszik mint az a narancssárga. Azt az okkersárgát nem szeretem." = "I like this (lemon)yellow skirt better than that orange one. I don't like that ochre one."