Original Design

Current Design
The image on top is from the Materials Collection. It is an early drawing of what Naoko Takeuchi originally envisioned Sailor Mercury's costume to be like. The image on bottom is from Artbook I. It is Sailor Mercury's outfit as it was determined to permanently look, and as we see it today.

Differences:
  The Tiara - it's gone in the original! Glad we got the tiara!

  The Collar - also gone! Poor Mercury seems to be missing out on a lot of things...

  The Outfit - whoa, her outfit is quite different from what it was destined to become. The collar has two stripes (it would later have three) and half of it is white. There are shoulderguards. The outfit has long sleeves with pink ribbons at the ends, and an empire waist with buttons on it. The skirt is also not pleated.

  Bows - the back bow is missing entirely. The front bow is very small, and pink, with a Mercury symbol on it.

  Earrings - in the original proposal, she had only one earring per ear, but her character developed three earrings per ear.

  Gloves - No gloves!

  Shoes - they are quite different! In the original proposal, she had small blue Mary Jane-style shoes with a green Mercury symbol on them. But they were later changed to permanently be tall blue boots, similar to Sailor Moon's.