The colors, in military usage, are the flag or standard of a unit — treated as the visible embodiment of its honor, never abandoned without disgrace. Scripture has the parallel. Israel encamped by tribes around the tabernacle, each tribe under its own standard: "Every man of the children of Israel shall pitch by his own standard, with the ensign of their father’s house" (Numbers 2:2). Christ is the ensign to whom the nations rally: "there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek" (Isaiah 11:10). The cross is now the colors under which the saints muster — emblem of victory by suffering, banner of the Lamb.
(Plural.) A flag, standard, or ensign; in military use, the official banner of a body of troops.
COLORS, n. plural. In military usage, the flag, standard, or ensign of a regiment.
‘Trooping the colors’, ‘under his colors’, ‘showing one's colors’ — the metaphors all rest on the visual standard around which a unit gathers and under which it fights.
Numbers 2:2 — "Every man of the children of Israel shall pitch by his own standard, with the ensign of their father's house."
Isaiah 11:10 — "And in that day there shall be a root of Jesse, which shall stand for an ensign of the people."
Galatians 6:14 — "But God forbid that I should glory, save in the cross of our Lord Jesus Christ."
Song of Solomon 6:4 — "Thou art beautiful, O my love... terrible as an army with banners."
Modern Christians often hide their colors; Scripture commands them to be raised and stood under.
Paul's ‘God forbid that I should glory, save in the cross’ (Gal 6:14) is colors-talk. The cross is the saint's standard; the household is enrolled under it; the church marches behind it.
Modern reluctance to be visibly Christian in public is a form of taking down the colors. Recovery is simple: raise them again. The cross at home, the confession in conversation, the prayer before the meal, the Bible on the desk — visible colors, no apology.
Hebrew degel (banner, standard, color) is the closest term.
Hebrew degel — standard, banner, regimental color (Num 2:2).
Note: cognate with the verb dagal (to hold up a flag, to be conspicuous).
"The cross is the saint's colors."
"Hiding the colors is a quiet desertion."
"Raise them again; no apology required."