Chesterfield inflicted Colchester's first defeat of the season after two goals from new signing Tcham N'Toya gave them a 2-1 win.
N'Toya's precise finishing was too much for Colchester
N'Toya gave his side a great start with a precise low drive after nine minutes.
Johnson equalised just before the half-time whistle with an untidy goal against the run of play.
But N'Toya scored again on 50 minutes, while Colchester's Stephen Hunt was sent off on his debut for a poor challenge on the 21-year-old striker.
Chesterfield: Muggleton, Bailey, Evatt, O'Hare, Nicholson,
Allott, Innes, Niven, Campbell-Ryce (Smith 60),
De Bolla (Folan 72), N'Toya.
Subs Not Used: Davies, Downes, Richmond.
Goals: N'Toya 9, 55.
Colchester: Davison, Halford, Brown, Chilvers, Stockley,
Keith (May 65), Watson, Cade, Johnson (Hunt 66), Andrews, Fagan.
Subs Not Used: Baldwin, Gerken, White.
Sent Off: Hunt (67).
Goals: Johnson 44.
Ref: A Hall (W Midlands).