Anthocyanin

The days are warming up. The soil is drying out. The plants are starting to wake up and grow. In some parts, they call it Spring.
There is the slightest hint of growth at the base of some of the perennial flowers. Future flowers curled up in tiny little baby bundles just below the mulch line and slowly stretching up toward the sun. Anise hyssop, lupine, angelica and columbine all ready to return for another year, along with dock and a dozen other unwelcome weeds. At this stage they are all purples and reds, with just a suggestion of green, usually down near the stem.
The poor little things are cold and they're hungry for any little scrap of heat available, and red leaves absorb more heat than green. They're trying their best to balance the red and the green, the heat and the food, doling out their budget ever so cautiously to cover the basic necessities. Chlorophyll takes back seat to a few other compounds this time of year, to make room for more antho- and caro- and xanthos. With a subsequent shift in hue. It's autumn in reverse. The leaves will become increasingly more green as the days warm - color as thermometer - and these tiny little buds now struggling so hard to stay warm will provide shade.