Greater Anglia operates a train from Colchester to Waterloo Station every 30 minutes. Tickets cost $23 - $35 and the journey takes 50 min. London Underground (Tube) also services this route every 5 minutes. Alternatively, National Express operates a bus from Colchester to Waterloo Station once daily. Tickets cost $9 - $13 and the journey takes 2 h 5 min.
From Colchester train to Stratford Underground Station then Tube to Waterloo Underground Station. 1 h 10 min £23. From Colchester bus to London Waterloo Rail Station then walk to Waterloo Station. 2 h 9 min £9. From Colchester Town Centre, St. John's Street bus to Chelmsford, train to Stratford Underground Station, then Tube to Waterloo Underground Station. 2 h 14 min £19. From Colchester drive to Waterloo Station. 1 h 15 min £11.
Yes, there is a direct bus departing from Colchester and arriving at London Waterloo Rail Station. Services depart once daily, and operate every day. The journey takes approximately 2 hours.