What does the colour purple refer to in Dickinson's "What care the Dead, for Chanticleer"?

This is one of many poems written by Emily Dickinson that
deal with the topic of death and the state of being dead. The opening question is
repeated throughout the poem in various guises, which serves to reinforce the way that
the dead exist in a realm that removes them from the cares of the living, such as the
seasons and the different kinds of weather and the summons of the crow in the early
morning. They have entirely different priorities from the living, the poem implies. Note
how the colour purple is used in the first stanza:

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What care the Dead, for
Chanticleer—
What care the Dead for Day?
'Tis late your Sunrise vex
their face—
And Purple Ribaldry—of
Morning

The colour purple is
therefore used to describe the "Purple Ribaldry" of the morning light as the sun rises.
What is interesting about the usage of purple in this poem is that normally in
Dickinson's poetry, purple is a colour that is associated with dignity and with emperors
or Christ's nobility. Here, it is coupled with an adjective that means "obscene" or
"coarse." Perhaps Dickinson suggests here that the beauty and splash of colour of the
sunrise can be considered obscene in the face of the solemnity of
death.