This trend really isn't about hijab or modesty because it's all about the colors. Grapefruit, lemon, lime - anything citrusy will do.
Sometimes, people are afraid to wear really bright colors because they don't know how to work them into their wardrobes. A good rule of thumb is that if the pieces are relatively small, you could do more than one in a bright color. For example, you could wear a bright hijab and a matching bag or shoe.
Alternatively, you could do one large citrusy piece and pair it with neutral colors. And I also love the idea of wearing a black abaya and popping it with a citrus colored hijab. What do you think?
(collage created using images from style)