First: The reason why I like this denim button-up in particular is because it tones down the formality of any outfit.
Second: Since the length on this one is the same as the skirt, it makes the two separate pieces more tied together as one unified outfit.
P.S. If you're the type that doesn't like too much color in your wardrobe but you still want to be in tune with spring, go for patterns instead. They add the same bouncy spring time vibe, but also come in black and white.