Red Scarab 
Enchantment — Aura
Enchant creature
Enchanted creature can't be blocked by red creatures.
Enchanted creature gets +2/+2 as long as an opponent controls a red permanent.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Green Scarab 81%
$0.27#25566
"Enchanted creature can't be blocked by green creatures."
+1 more matching line
Blue Scarab 81%
$0.25#24760
"Enchanted creature can't be blocked by blue creatures."
+2 more matching lines
Black Scarab 81%
$0.22#24359
"Enchanted creature can't be blocked by black creatures."
+1 more matching line