Anthocyanidin

They are based on the flavylium cation,[1] an oxonium ion, with various groups substituted for its hydrogen atoms.

They generally change color from red through purple, blue, and bluish green as a function of pH.

At least 31 monomeric anthocyanidins have been properly identified in living organisms, mostly as the core components of anthocyanins.

Altogether 20% of the anthocyanins are based on the three common anthocyanidins (peonidin, malvidin, and petunidin) that are methylated.

Both pigments were also detected in the liverworts Marchantia polymorpha, Riccia duplex, and Scapania undulata.

Molecule in 3D of the anthocyanidin cyanidin
Stability of anthocyanidins is dependent on pH.
Stability of anthocyanidins is dependent on pH .