Allowing your bridesmaids to choose their own dresses guarantees they'll feel beautiful and comfortable. You have two options: Ask them to choose dresses in the exact same color, or in varying shades of that color. Set some ground rules, though: Provide them with fabric swatches—or even paint chips from the hardware store—to illustrate the range of colors you want to achieve. For maximum clarity, specify a dress length and fabric type (for example, tea-length, in cotton) to keep the looks consistent.
See, it works!
Kristina's bridesmaids wore green dresses in shades and styles they chose themselves.