What color plug where i ve got three colors blue,red,black

If I understand correctly, you are replacing a switch with the EJ500 timer.
You mention a 'plug'

The EJ500 has 3 wires: Black Red Blue.
If you are replacing a single-pole switch:
The switch has 2 wires, one of these wires is the Hot-from-breaker and the other wire goes to Load:
Timer-black connects to Hot-from-breaker.
Timer-blue connects to wire-going-to-Load.
Timer-red wire is capped off. Red is not used for single pole switch.
If you connect wires and your lights blink, then you put the red wire where the blues wire should go.
If you connect wires and lights do not operate, try reversing the blue and black wires.

I posted images of EJ500 wiring (the Intermatic EJ500 and ST01C have identical wiring
http://waterheatertimer.org/ST01C-program.html#ST01C

If you are replacing a 3-way switch, the wiring is more complicated.
The EJ500 can not replace a 3-way switch wire-for-wire.
Diagrams on link above show wiring for 3-way.
Add a comment if you need more help.