olive green semi formal dress Simple Backless Long Prom with Slit, Evening Dress, – AlineBridal The short length of the dress makes it perfect for cocktail parties or semi Linen Blend Shirred Handkerchief Hem

You could also add shape via color, like the blue and red dress below

Loafers or chukkas probably

Unless the invitation says otherwise, its always best to avoid the color white (or anything similar, like ivory) for a wedding

BABYBOO Petal & Pup Xavier Bow Strap Satin Gown (Women) | Nordstrom Nordstrom Azazie A-Line/Princess Scoop Neck Floor-Length Floral Burnout Bridesmaid Dresses - Dark Navy Azazie Navy blue formal dress size 14 Gorgeous navy blue formal dress with boning and lace up corset back brand new never used size 14 perfect for a wedding

They are comfortable enough to wear all day while looking glamorous