Synonyms for Sombre (same or very similar meaning)
WordNet sense 1 (lacking brightness or color; dull):
drab, sober, somber
WordNet sense 2 (weak in color; not colorful):
colorless, colourless
WordNet sense 3 (grave or even gloomy in character):
melancholy
WordNet sense 4 (lacking cheer; depressing):
cheerless, uncheerful
From the ODE community, based on WordNet
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