A thing is either blue, or it isn't. It can't be "falsely" blue.
Dear Charles,
Is the sky itself, then "truly" blue? Its color, as I understand it, is the result of reflection, and so "falsely" blue describes not only the window reflecting the sky, but the sky itself. Assuredly the sky has not pigment - - so is it blue? In butterfly wings the blue color is produced by the angle at which the scales lay.*
Besides the intended meaning of "false azure" as used in the poem is certainly clear, or should be.
Carolyn
* "New research shows that the wings of the morpho rhetenor butterfly reflect its brilliant blue colors not from pigment but from extremely small scaffolding within the scales of the butterflyıs wings."