From the story's prologue:
[Ennis] gets up, scratching the grey wedge of belly and pubic hair, shuffles to the gas burner, pours leftover coffee in a chipped enamel pan; the flame swathes it in blue. He turns on the tap and urinates in the sink, pulls on his shirt and jeans, his worn boots, stamping the heels against the floor to get them full on.
This starts the story out on a depressing note. Ennis is a washed up guy who shuffles, settles for warmed over leftover coffee, pees in the sink, and hurriedly pulls on worn boots. The only thing that stands out here is the flame that swathes the coffee in its blue flame. Blue is a reminder of Jack, and the flame tells us that Ennis still carries the torch for Jack after all these years.