What methods promote color changes in hydrangea flowers?

Hydrangea is a plant of the Saxifragaceae family and the Hydrangea genus, with emerald, glossy leaves and large inflorescences, and its flower color is highly variable. It is one of the potted flowers increasingly favored by city residents in recent years. Because of differences in the soil or medium used for planting, as well as the organic fertilizer or nutrient solution applied, it displays different flower colors, and will change with the variation in acidity and alkalinity in the soil or medium. Petal color generally changes from dark to light, that is, from light purple and blue gradually to water red, and even white. When the soil or medium shows an acidic reaction, the flower color appears deep blue or light purple. When the soil or medium shows an alkaline reaction, the flower color appears water red. During cultivation, according to your preference for flower color, you can regulate the pH value of the soil through water and fertilizer with different acidity and alkalinity, so that the flower color shifts toward the color you like. For example: you can first use pH test paper to measure the true pH value of the soil. A pH value between 6.5 and 7.5 is neutral soil, a pH value between 5.0 and 6.5 is acidic soil, less than 5.0 is strongly acidic soil, a pH value between 7.5 and 8.5 is alkaline soil, and higher than 8.5 is strongly alkaline soil. To promote deep blue flower color, during the bud stage, apply a small amount of aluminum sulfate, sulfur powder (100 grams/cubic meter to 200 grams/cubic meter), edible rice vinegar (200-fold to 300-fold solution), ferrous sulfate (0.3%), etc. If you want the flower color to become pink, add a small amount of lime powder to the soil, or use an alkaline wood ash solution to regulate it, which can shift it toward a slightly alkaline state and make the flower color appear deep blue or light purple.