Waterproof apparel constructed of a flexible PVC sheet or other polymeric flexible sheet material that changes color due to a change in ambient conditions. Thermochromic dyes and/or photochromatic dyes are incorporated into the resin mix for fabricating the flexible sheet material. The color of the waterproof apparel changes when the temperature rises above or drops below a pre-defined temperature and/or when the ultra-violet light level is above or below a pre-defined level.