When considering the Yoko Hi Vis 2 Band and Braces Vest you should place the different colours of this vest into two groups. In the first group are the Yellow, Orange, Yellow-Orange, and Two-Tone colours.
This group conforms to EN ISO20471 which is an international standard for safety requirements of high visibility workwear. If your work requires conformity to this standard or you simply feel safer using gear that follows this standard, choose from this group only. The other colours are simply high visibility clothing. Within the EN ISO20471 standard there are several classes. Class 1 refers to the lowest level of visibility and requires at least .10 sqm of reflective tape and .14 sqm of fluorescent material.
Class 2 is an intermediate level of visibility requiring at least .13 sqm of reflective tape and .50 sqm of fluorescent material. Yellow, Orange and Yellow/Orange variants of this vest are Class 2. Two Tones are Class 1.