The phrase "are red when" is correct and usable in written English.
It can be used to describe a condition or state that occurs under specific circumstances, often in scientific or descriptive contexts.
Example: "The leaves are red when the temperature drops in autumn."
Alternatives: "turn red when" or "become red when".
"The ears are red when they're backlit.
That's why they are red when I am photographed with a flashbulb.
The planes denote a correlation difference of zero and are red when the confidence intervals pass through zero, indicating that the actual difference between the two compared methods might be zero.
G402 cells are red when adenine is limiting due to accumulation of a metabolite of the adenine biosynthetic pathway.
The nitrogen catabolite regulator Ure2p represses the DAL5 promoter when a good source of nitrogen is available, so on standard growth media containing ammonium ADE2 expression is repressed and, like ade2 1 mutants, cells require exogenous adenine to grow and are red when adenine is limiting.
Nonsuppressed ade2-1 mutares adeninenine auxotrophs and are red when grown on adenine limiting media.
Gold, which is used often in medicine, is red when broken down into tiny particles.
"Witnesses also testified that the traffic light was red when Spellman's car approached the intersection and struck the victim.
I've had someone rush in to powder my nose because it's red when the character is broken-hearted and crying.
Periodically, he would call out instructions, like, "Can you make it cold white, and then start bringing it down?" or, "You know, the easiest is red — when in doubt, make it red".
"You can't say that the light was red when everyone else is saying the light was green," Justice Charles E. Ramos told David Boies, the well-known litigator who has represented Mr. Greenberg since his ouster from A.I.G. in 2005.
