I heard a Fly buzz – when I died –
The Stillness in the Room
Was like the Stillness in the Air –
Between the Heaves of Storm –
The Eyes around – had wrung them dry –
And Breaths were gathering firm
For that last Onset – when the King
Be witnessed – in the Room –
I willed my Keepsakes – Signed away
What portions of me be
Assignable – and then it was
There interposed a Fly –
With Blue – uncertain stumbling Buzz –
Between the light – and me –
And then the Windows failed – and then
I could not see to see –
The noun “Blue” is difficult to interpret. Flies are often coloured blue-black, but this is too literal.  Furthermore, “blue” to mean sadness wasn’t in use in the nineteenth century. So, this “Blue” is what the fly is blocking; the blueness of the sky through the window which the spirit will reach towards on the journey to the afterlife. 
 That the fly is “stumbling,” zigzagging back and forth “uncertain,” represents the speaker’s faith and her uncertainty. 
 The blending together of blue and buzz — colour and sound — is an example of  synaesthesia .
I heard a Fly buzz 465