what about darker like slate?

While "Jack-O-Lantern orange" might not be appropriate for the new bath, if you like the orange family there's absolutely no reason you couldn't have an orange if you wanted to. If your white marble has a blue tone they'll both "pop" each other, since orange and blue are opposites on the color wheel. I like the idea of the apricot, although a Creamsicle or cantaloupe color - a diluted, softened version of the Jack-O-Lantern orange - would go beautifully with the black and white too. And no, there is no reason why there would be much of a problem at all with a green hallway and an orange bathroom: think of all the plants with orange flowers and green foliage out there, and how wonderful that looks! Mother Nature never goes wrong with Her color combinations.

If you do decide to go with gray-blue, Eddie Bauer "Slate" from Lowes is a great color - it has enough gray in it to keep it from going "baby blue" but OTOH it has enough blue to keep it from being too somber. It's more of a midtone so it doesn't wash-out, and it goes very nicely with black and white. But I agree it's a bit safe, and it does sound like you prefer the warmer colors, so go with what makes your heart go pitter-pat.

There is a pic of a period bath in this thread that uses a warm yellow color on the walls - gorgeous! There's another thread out there somewhere with a pic of a bath done in the apricot color you're referring to and it is GORGEOUS - I'll try to dig it up, but in the meantime, check this one out - it's about halfway down the thread.

Here is a link that might be useful: Yellow bath thread

My original plan for our bath was celery green on the walls and the back of the door tangerine orange (or cherry red depending on my mood).

But somewhere along the line we somehow got into the restoration hardware silver sage vibe and I'm happy with it, but do kind of think sometime in the future ...

If you decide on something more subdued we did RH's pale silver on the wall and silver sage for the back of the door. Pale silver is a bit greeny so it might go well with the green you've got.

Ginabee - We just got done with our bath that has similar elements (white tile w/ black accents, marble, white wainscoting). We used Restoration Hardware's Atmosphere Blue and it came out really nice IMO. It's a greyish blue, like you're considering. Our adjoining bedroom is celadon.

Emily

So what did you pick?

I have white beadboard, the floor is Dal Tile's Chloe which is a pinwheel design in white & black. The walls are painted BM Yarmouth Blue. The color reminds me of the beach ... a mix between the intense blue of a southern spring and fall sky and the clear blue water along some beaches.