What plants change colour due to pH?

Certain plants, particularly some species of hydrangeas, change color in response to soil pH. For instance, hydrangea flowers can appear blue in acidic soil (pH below 6) and pink in alkaline soil (pH above 7). Additionally, some varieties of litmus plants and certain types of orchids can also exhibit color changes based on pH levels. This phenomenon is due to the presence of anthocyanin pigments, which react differently in varying pH environments.