Crimson sits next to 3 phonetic neighbors — Crystal, Carmen, and Crispin are the closest matches by sound. Most share Crimson's English-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"deep purplish-red color"
"of Mars, belonging to the war god"
"descendant of the king"
"noble, of noble kind"
"possessing goodness"
"dark, rich one of God"
"dry-loving flower"
"rhythm, musical flow"
"exaltation (Selah)"
"from Wales, land of Cymry"
"fairy, enchanted being"
"snow"
"form of Michael/Micaiah"
"beloved, little love"
"joyful, playful"
"calm, serene"
"rival, emulator (via Camilla/Aemilia)"
"high chief of heaven"
"short form of Nicholas/Nicola"
"bright, clear (Clara) + beautiful (Belle)"
"gift of God"
Similar sound: These names share phonetic patterns with Crimson — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Arabic qirmiz via Medieval Latin origins, giving them the same cultural heritage as Crimson.
Rhythm: Crimson is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.