Dorian Gray (cool name) looks like a good color. I also have a gray house that needs to be painted this year. I don't like blue grays and definitely not purple grays. If I have to lean towards an undertone, I prefer green, which DG appears slightly to me.

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).

would manchester tan be a good choice

Bright white trim with Dover White. Had many rooms in my home painted this color to prepare for sale. Looked great, sold fast, great price. My painter loved it and started using it for his other customers. This house was in Florida... don't know where you're from but would consider the quality of the light in your area. This color worked well with tiled floors (warm neutral), hickory hardwoods, and grey carpet in an office. I even used this color outside to freshen up the stucco in the entryway and the lanai. Hope this helps!