Solution 1: For mismatched chairs, paint them all the same color. This will give the dining room a unified look, but each chair retains its personality with its varying shapes and lines.
Solution 2: For matched chairs, paint them all different colors. We like the look of strong primary colors (red, yellow, blue) with black and white for a graphic, Mondrian-inspired look. Or, if you'd prefer to stick to one color but want a little bit of diversity, pick 4-5 different shades to create a subtle, Pantone-esque gradient of chairs around the table.
Solution 3: For mismatched chairs, stick to a tight range of shades. This particular example has a hodge podge of chairs and stools, all in a range of light blonde to a dark walnut wood finish. If you're not a fan of the painted look, this is certainly a more natural-looking solution although it might take a bit more elbow grease with prepping and sealing. We'd suggest narrowing the color selection by using one wood stain for every two chairs to keep the look balanced.