The word "reddish-grey" refers to a color that is somewhat difficult to describe, as it blends both warm and cool tones. Its antonyms, however, can provide a clear idea of what colors are opposite to reddish-grey. Firstly, on the warm side of the spectrum, we have yellow and orange, both of which represent energy, happiness, and vibrancy. On the cool side, we have blues and greens, which are calming, serene, and refreshing. Finally, the neutral colors of black and white provide a striking contrast to reddish-grey, with black being bold and dramatic, and white providing a clean and minimalist look. Together, these antonyms showcase the various colors that can juxtapose the unique blend of reddish-grey.