That burnt orange and rust plaid pocket square is a fantastic choice for fall-inspired or earth-toned outfits. To make it pop without clashing, you'll want a suit color that either provides a sharp contrast or complements its warm tones. 
Here are the best suit colors to pair with it:
Dark Brown or Chocolate: This creates a sophisticated, tonal look that leans into the "autumn" aesthetic of the fabric. It’s a very cohesive combination.
Charcoal or Dark Grey: The cool tone of a dark grey suit provides a sharp, modern contrast that makes the warm orange and rust shades really stand out.
Navy Blue: Orange and blue are complementary colors on the color wheel. A deep navy suit will make the pocket square appear even more vibrant while maintaining a classic, professional feel.
Olive or Forest Green: For a rich, earthy look, a dark green suit works beautifully with rust and orange tones, especially during the fall or winter seasons.