Question

a. what is the relationship between color and surface temperature? b. what is the most common element(s) identified in the stars spectrum?

Explanation:

a. Generally, cooler stars appear red - orange, while hotter stars are blue - white, so there is a correlation between a star's color and its surface temperature.
b. Hydrogen is the most abundant and commonly identified element in a star's spectrum as it is the fuel for nuclear fusion in stars.

Answer:

a. Cooler stars are red - orange, hotter stars are blue - white.
b. Hydrogen.