Final answer:
The amount of sunlight and the concentration of nutrients are the two variables that determine which colored protist thrives in an area.
Step-by-step explanation:
The amount of sunlight and the concentration of nutrients are the two variables that most strongly contribute to the type of colored protist that thrives in an area. Light plays a crucial role in the distribution of photosynthetic organisms in both terrestrial and aquatic environments. In aquatic environments, light intensity is influenced by the depth and transparency of the water, which directly affects the presence and growth of colored protists. Additionally, the concentration of nutrients in the water determines the availability of essential resources for protist growth and survival.