I have tried to delay the frosts, I have coaxed the fading flowers, I thought I could detain a few of the crimson leaves until you had smiled upon them; but their companions call them, and they cannot stay away.
— Emily Dickinson, letter, 1851
Crimson and carmine, words for deep reds, are doublets from the same Arabic source. The color crimson is a deep purplish red that is found in a dye made from pulverized kermes, or the dried bodies of insects. The name of the color and of the insect has been traced back to qirmiz, the Arabic name for the insect. The word crimson entered English in the 15th century via Old Spanish cremesín.
In the 18th century, carmine arrived in English via French as a synonym of crimson. The French derivative is from Medieval Latin carminium, which has also been traced to Arabic qirmiz. The Latin form was more than likely influenced by minium, which refers to an artificial red sulfide once used as a pigment.
Like scarlet, crimson has figurative use associated with sin that originated in the Book of Isaiah via a continuation of the verse quoted above: "Though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool." In particular, crimson has come to describe acts of bloodshed. William Shakespeare used the word with such connotation in Richard II:
If not, I'll use the advantage of my power and lay the summer's dust with showers of blood Rain'd from the wounds of slaughtered Englishmen; ... It is such crimson tempest should bedrench ... fair King Richard's land.
Considering this bloody figurative sense of crimson and the fact that crimson and carmine are connected to a dye made from dead insects, it seems applicable to use both words during the spookiest time of the year.