Gray wall paints come in values from airy light tints to deep charcoals, and are typically either warm or cool. An array of nuanced color undertones provide the variations in gray paint colors. Depending on color, undertones will show more apparently on a wall than others. Always be sure to try a sample of the color on your walls. Since light from outside sources strikes walls differently, try the sample on all walls where you plan to use the color; you don’t want any surprises. (Always paint on a white background as colors affect other colors: see this at my post The Changing Nature of Color.) Here are a few sample gray paint colors from light to dark; you can see the nuances in undertones.
Top row: Sherwin-Williams Mindful Gray SW 7016, and Silver Strand SW 7057. Benjamin Moore Graytint 1611.
Bottom row: Benjamin Moore Misty Gray 2124-60. Dunn Edwards & California Paints Faded Gray DEW 382, and Formal Gray DE6382.