I think I like this thread because my front porch is my favorite part of the house
As i think about it, if the shade of the back/side deck sort of blended in with the house (it's already stained grey, is it a simillar shade to the siding?) and you did the front porch with the white rails and finished wood as an accent, it would seem to me it could maybe work... it's still hard for me to be sure, but i can sort of picture something like this...
Back/side porch sort of blending in in grey.... white rails and posts to go with the house trim, natural wood finish on the porch floor and the tops of the steps, maybe the same grey stain as for the back for any wood that is not a horizontal surface on your front porch, to tie it in with the back deck. of course, that would be three tones, white trim, wood floor, and grey for the step risers and such, but depending on the style of house, i think it could be cute. Particularly with a cranberry door.
But...
You should probably be warned that I own a little cottage and don't subscribe to the two-color theory. Once I get a few other things done and get to painting my house, it will be pale yellow with white trim, very dark green window sashes and porch floors, and a crimson roof and door. Of course, there are a few people that think I'm nuts too.
The important thing is this.. what will YOU like? I guess if you painted the front porch rails white to match your house trim, the absolute worst thing that could happen is that you would end up painting the rails on the back/side deck to match later. Unless it doesn't have rails, in which case, the problem doesn't seem that big to me.
Oh... I tend to like lighter stains myself... because they just look brighter to me.