The color of the TechNiche HyperKewl Cooling Vest should make no difference in its ability to work the way it is designed. If you feel a lighter color like silver would be less heat absorbing you can certainly go with that color vest for use.
The TechNiche HyperKewl Evaporating Cooling Sport Vest works for many uses and requires exposure to airflow but can still be used in dry heat weather.