Final answer:
NASA used International Orange color for space shuttle suits to ensure high visibility during launch and entry phases of space shuttle missions for safety reasons.
Step-by-step explanation:
The color shade used by NASA for its space shuttle suits was International Orange. This color was chosen for the suits worn during launch and entry phases of the space shuttle missions because it was highly visible in various environmental conditions which could be critical during an emergency situation. While in space, astronauts would wear different suits for their extravehicular activities, commonly known as spacewalks, which were white to reflect sunlight and minimize temperature extremes.