Flowers can change color when moved to a different location, when under stress from temperature (colors are often more vivid in cooler northern gardens than in hot southern ones); also drought, insects or plant nutrition can result in differing levels of pigments in flowers and, thus, differing colors. It may be your soil pH. Peonies prefer 6.0 to 7.5 pH. You could check the soil and adjust accordingly; see here: http://www.almanac.com/content/ph-preferences (Note that changing the pH may or may not have an immediate effect on the flowers.)
Flowers can change color when moved to a different location, when under stress from temperature (colors are often more vivid in cooler northern gardens than in hot southern ones); also drought, insects or plant nutrition can result in differing levels of pigments in flowers and, thus, differing colors. It may be your soil pH. Peonies prefer 6.0 to 7.5 pH. You could check the soil and adjust accordingly; see here: http://www.almanac.com/content/ph-preferences (Note that changing the pH may or may not have an immediate effect on the flowers.)