I'd start with his favorite color and yours, then go from there.... Have fun, and enjoy yourselves! Bright colors photograph well, and a color wheel can give you ideas of what colors complement each other. Also, check what flowers are in season in May to help give you ideas. Just do what you love, and have fun.
Begin with what inspires you! Do you love long walks on wooded paths? Yes? Then spring green & sky blue may move you. Are you more of an urban chic woman? If so, than think clear glass, mirrored silver & racy red. Does a favorite flower cheer you up? Sure? Then pale peony pink or blushing cherry blossom could be the perfect touch. If your hobbies or passions don't put you on the right color track, try calling a planner who offers design services. Me. Good luck to you!