The PC disk changes color
from red to black to signal the user that it has expired.
Using a tiny sample of tissue, the test solution changes color
if the fish contains as little as half the recommended FDA limit of mercury.
A portion of the strip changes color
to show the amount of moisture absorbed by the brief.
A chameleon also changes color
when it gets scared or angry.
This erudite discourse then explores the various forms and functions of skin, including how it changes color
and how those colors are ascribed to different feelings and conditions: green for envy, purple for rage.
It's basically as simple as using litmus paper to see if a solution is acidic or basic by observing whether the paper changes color
. In smell-seeing, the dyes are vapor-sensitive metalloporphyrins that are closely related to hemoglobin, which transports oxygen in blood, and chlorophyll, the green pigment in plants.