Red

|First colour perceived by infants at five months of age
|Visibility at wavelengths of 625–740 nm

flush [fləSH] VERB
1 (of a person’s skin, face, etc.) become red and hot, typically as the result of illness or strong emotion.
synonyms: ruddy · glowing · florid
2 (of a plant) send out fresh shoots

https://www.lexico.com/en/definition/liminal