If it is a standard T1 decoder (not the T!-LED), you will need to add your own resistors to the LEDs. A 1000 ohm resistor is typical.
On ALL decoders, the blue wire is the common (positive voltage) and the white and yellow wires are the voltage sinks (or negative).
LEDs have two different lead lengths, the longer one is the positive (blue wire) connection.
By default, the front and rear lights are directional, controlled by F0 on your throttle.
Mark.