If you like the plain black dress, then it would be best for the night functions.
However, if you have enough them or want to add a spark in your clothing design, there are a number of black dresses with the floral combinations in print. This can give you a lively look as well as diversify your wardrobe.
Apart from black, colors like lighter shades of green, orange salmon, white and subtle red are some of the prominent options that you can have.
These ones are appropriate for the daytime event. Using these colors would give an impression that you know fashion and how to carry the colors for a particular season.