Colchester to Romford is priced between £15.80 and £26.10 for a return, depending on time of travel.
Splitting is less likely to work where the journey is on one operator, and for short to medium (ie, not long) distance journeys, on linear routes plus branches. I looked at splitting at Chelmsford and Shenfield, and in both cases there wasn't any benefit on the (Super) Off Peak Day fares. Splitting means you can't get an Off Peak Return (SVR) to return a different day, however I did discover that if you wish to travel at peak time, it is cheaper so split at Chelmsford.
Colchester-Chelmsford SDR £10.80
Chelmsford-Romford SDR £13.00
Total £23.80
A small saving compared to the through SDR fare of £26.10