Do you have any wood siding or is the house entirely brick? You could go with a gray stain to pick up the grout color, or a warm wood color to mimic the warmth of the bricks. Have fun!

You would be amazed on how well contrasting wood stains accent one another the deck should be at least 3 to 8 tones deeper then the rails if they are natural wood stain color I just did a job like that it came out fantastic and warm looking do not do it brick color I feel that would be ugly keep it to mother nature of the forest tree