There really is no substitution for testing the colors in your space and different light through the day. For a suppposedly neutral color, greys can be tricky. Fact of the matetr is that a greyy can be any color plus black or some canceling tones. Revere Pewter goes violet on me and Edgecomb grey a bit green in some rooms. I wound up going to Sherwin Williams and trying their colors. Agreeable Grey was the right tone for my living areas, but I am doing them at 150% to get a little deeper color. I am using Anew Grey in my entry and stairwell -- that hasn't been done yet. . More important to your question about going with cool and warm colors -- the Agreeable Grey in my FR had to work with red brick, cherry hutch and dark wood floors as well as blue, green and white in the upoho;stery, rug and kitchen cabinets and counters. Anything that tended green made the red brick fireplace more intense and anything too warm made it pinker/orangier. Agreeable Grey at 100% was too light -- was too close to my grout and looked chalky, so we just added more color and went to 150%. SInce it is a light color to begin with, it is still light, just richer. The result was amazing -- my red brick calmed down. No more orangey, purpley/brown red. And it is so soft and neutral with the blues,, green and white. We did the ceiling at a reduced value. It was the first time I had used SW paints and as much as I liked BM, I was just as pleased with this job (DIY).

I would probably stick with one color for both rooms, if it were me. I instantly thought of BM Grey Owl for what you are describing. It is slightly blue-green while still being a warmish grey. I love it, but it was too blue to pair with my pinkish carpet in my house (didn't want a pastel color combo going on!) I also like SW Passive, but it is a little cooler. If you do the blue kitchen, I would caution against a warm grey with too much pink in it (the baby room effect). I'm definitely no expert, but I just bought my first home too and have spent MONTHS researching grey paint! I ended up selecting SW Useful Grey. It is a greenish grey, which I never thought I'd pick. I guess I'd just suggest taking your time and keeping an open mind when looking at colors :) And definitely buy samples to test in your home...

Select your colors from you tile....lightest tone for trim, and the next darkest for walls. If these is a paint consultant for hire in your area that might be a good investment as paint can drive you crazy.....also a good paint contractor has seen it all and can give you some pointers too....but a designer might be your best bet.

Echo others in that we need to see other existing finishes, and understand more about the light situation. It can also be that in the current hot market you need just to touch up the existing paint/paint when needed, instead of completely redo it. I don't know whether I believe there is magical color X that will work anywhere just the same. Some colors tend to work better in houses such and such in geographical locations such and such, and thus become a staple. But we don't know enough about the location or the house style.