Stephen Crane's short story "The Open Boat" begins in the following way:

None of them knew the color of the sky.

In looking at this line only, without looking at the sentences which follow, one could infer a few different things.

First, one could assume ignorance. This could be identified as being that the speaker is ignorant of what color is or how to identify a color.

Second, one could infer that they were unable to see the sky. They may be sheltered from the sky; although the title would speak against this idea ("open boat" refers to no roof being present). Another reason could be that the boat's inhabitants were not looking at the sky. They may not be concerned with the sky, or their focus may be on something else (which the narrator tells readers in the sentences which follow).

Lastly, readers do not know the predicament of "them." While, based upon the title, some readers may correctly assume that the characters are on the water in a boat, the line in question does not give enough information about where the characters are in the boat. The characters could be in the water under an overturned boat; therefore, they cannot see the sky as it (the sky) is hidden from their view.

The sentences which follow the opening sentence allow readers to understand what the circumstances actually are—the men are too concerned with the storm and their eyes are focused on the waves before them.

"NONE of them knew the color of the sky. Their eyes glanced level, and were fastened upon the waves that swept toward them. These waves were of the hue of slate, save for the tops, which were of foaming white, and all of the men knew the colors of the sea. The horizon narrowed and widened, and dipped and rose, and at all times its edge was jagged with waves that seemed thrust up in points like rocks. " (Stephen Crane; "The Open Boat, pg 728)

In the first sentence of the story we are drawn into the struggle of the survivors of a boat in a storm so bad that they can't do anything but row and bail.  They can't even see the sky, all they can see is wave after wave.  It is night for one thing.  The very next part of the story indicates that the sun begins to rise.  This opening sentence makes the reader realize that the situation is intense and we, like the occupants of the boat are in for a terrible ordeal.  They are intent and focused so hard on the waves that they share with the reader their desire to live.