Most likely for Christmas
but there are other meanings.
Red light bulbs have various meanings. From good to not so good
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American Heart Health Awareness
Landmarks across the globe turn their bulbs red in February in honor of heart wellness awareness month as suggested by the American Heart Association.
During this month, the organization also encourages people to use their porch lights as a way of showing their support for heart health and to raise awareness.
put on the red light - Wiktionary, the free dictionary.
Etymology
Refers to the fact that a red light is traditionally placed in the windows of sex-related businesses; compare red-light district.
put on the red light (third-person singular simple present puts on the red light, present participle putting on the red light, simple past and past participle put on the red light)
(idiomatic) To advertise oneself as a prostitute.