-40% is the change from 255 to 153
Calculation steps:
[( 153 - 255 ) ÷ 255] x 100 = -40%
Formula
Percentage change = [(153 - 255) / 255] x 100
Subtract the new number by the original number
153 - 255 = -102
-102 ÷ 255 = -0.4
-0.4 x 100 = -40%
Example