Ever heard of a sand ceremony? This is a popular ritual for couples and families and sometimes couples children that want to express their unity in a symbolic way, by pouring coloured sand from separate vessels into one container. Typically each person has a different coloured sand.
It is a ritual that is usually enacted either after the vows or the ring exchange or after the pronouncement. However there are no hard and fast rules.
I will have coloured sand available for you to practice, as pouring sand from a vessel into one vessel at the same speed of pour is harder than you think… check out this website