I wrote it up this morning, originally thinking of including something about Iris, the Greek goddess of the Rainbow, and messenger of the gods. While she is described as one of the Greek goddesses, she ends up working more as a messenger. So, that wasn't quite a good fit, and then I discovered Harmonia, the goddess of harmony and concord.
The big problem is that Greek gods are often more flawed (or cursed) than the humans worshiping them, and not always a good choice for representing a certain ideal
Here's one of the better images of Harmonia (with the other Kharites) and a description:
Detail of three of the younger Kharites - Eudaimonia (Happiness), Harmonia (Harmony) and Paidia (Play) - , from a painting depicting the retinue of the goddess Aphrodite. Other figures in the scene (not shown) include the Erotes (Loves), Eurynoe, Pannychis (Night Festivity), Chrysothemis (Golden Custom), Hygieia (Good Health), and Pandaisia (Festivity).
HARMONIA was the goddess of harmony and concord. As a daughter of Aphrodite, she presided over marital harmony, soothing strife and discord; as a daughter of Ares, she represented harmonious action in war. Late Greek and Roman writers sometimes portrayed her as harmony in the more abstract sense : a deity presiding over the cosmic harmony.
Harmonia was born of Aphrodite's adulterous affair with the god Ares. She was awarded to Kadmos, the hero founder of Thebes, in a wedding attended by all the gods. Hephaistos, however, was still furious over his wife's betrayal, and presented Harmonia with a cursed necklace, which doomed her descendants to endless tragedy.
A string of family catastrophes caused the couple to emmigrate to Illyria, where they battled various local tribes to establish their new kingdom. Later the pair were turned into serpents by the gods and transferred to the Islands of the Blest, to live in peace and harmony for the rest of eternity.