Using colored flags helps me to visualize and place things in the garden. I use colors to represent different seasons or time periods:
BLUE – Earliest (Winter and earliest Spring)
GREEN – Early-mid (Spring/Early Summer)
YELLOW – Mid (Summer)
RED – Late (Fall)
When it comes time to plant a garden we use the flags to mark the areas and visualize decisions we've made on paper. It is easier for me to see the abstract patterns of the flags and imagine a garden moving through the seasons than to look at plants in pots.