Question

while the pennies are drying, put the paper clips in the bowl of solution. let them soak until their changes from silver to copper. it may take more, so be patient! shape color taste

Explanation:

The sentence is describing a change from silver to copper, which are colors. "Shape" would refer to a change in form, and "taste" is not relevant here as paper clips are not tasted. So the correct word is "color" as it fits the context of a change in the appearance related to hue.

Answer:

color