Poem Beach Burial do you know what this similie emphasises? "As blue as drowned mens lips" PLease help me!

Question

This is the poem...please help me!

Softly and humbly to the Gulf of Arabs

The convoys of dead sailors come;

At night they sway and wander in the waters far under,

But morning rolls them in the foam.

Between the sob and clubbing of gunfire

Someone, it seems, has time for this,

To pluck them from the shallows and bury them in burrows

And tread the sand upon their nakedness;

And each cross, the driven stake of tidewood,

Bears the last signature of men,

Written with such perplexity, with such bewildered pity,

The words choke as they begin -

"Unknown seaman" - the ghostly pencil

Wavers and fades, the purple drips,

The breath of wet season has washed their inscriptions

As blue as drowned men's lips,

Dead seamen, gone in search of the same landfall,

Whether as ememies they fought,

Or fought with us, or neither; the sand joins them together,

Enlisted on the other front.

Answer 1

After someone is dead, their lips turn blue. The inscriptions on the crosses have been changed by the weather, the same way a person's lips would be changed in death. The reference to drowned men, in particular, is because the inscription is specific to sailors.