Green flag

n.hopeful, thoughtfulplayful

What it means

A sign that someone or something has healthy qualities.

Reach for it when naming an encouraging sign of healthy qualities or likely compatibility

Her respect for clear boundaries was an immediate green flag.

everyday
positive sign
plain wording should mark favorable evidence
not when Positive sign is neutral and lacks green flag's contrast with a warning sign.
warm
encouraging sign
early evidence supports hope without proving an outcome
not when Encouraging sign is more cautious and may concern progress rather than character.
professional
favorable indicator
a measured signal supports a practical assessment
not when Indicator sounds analytical and is too impersonal for relationship advice.
professional
healthy signal
behavior suggests sound boundaries or practices
not when Reserve healthy signal for evidence about wellbeing or sound practice; ordinary preference needs no health claim.
formal
vote of confidence
another person's support strengthens trust
not when A vote of confidence is an endorsement, not a quality discovered in the subject.
literary
good omen
a sign appears to predict good fortune
not when Omen suggests fate or superstition, while a green flag may be observable behavior.

clear green flag
Respect for a stated boundary is a clear green flag.
major green flag
Her willingness to correct the mistake was a major green flag.
see as a green flag
Many candidates see published salary ranges as a green flag.

Green flag is informal and context-dependent. One positive sign does not establish a person's entire character or an organization's safety.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.