The decoder is a BLI factory installed board. It is with sound. The board ID is BLI N-100-D. The wire colors do not follow to the NMRA recommendations.
Along with what Henry has said, the decoder manual should also have a clue as to what you need. It probably will involve the green and violet wires, and you need at least a 4 function decoder to use them for "lighting effects".
What decoder do you have? Make and number? Usually the second number of a decoder is the number of functions it supports.
I cheat with ditch lights, because I usually use a 2 function decoder ( I'm cheap) and use pico size surface mount leds, with the resistor wired in. In the most basic control form, 1 wire from the prewired leds go to the "+" side, and the other to the "-" side. I have no control of the on and off wired this way, when track power is on, the ditch lights are on.
I'm far from a decoder expert, and others will chime in with more technical info.
Mike.
My You Tube
Decoders that have additional functions for ditch lights, mars lights etc, have additional soldering pads for each function. Possibly labeled F1, F2 etc The blue wire is the common wire used for all lighting.
I looked at various manuals on the BLI site and I don't see a pic of the decoder in your unit.
If you are asking what led's to use, they would be the really small ones. Someone will know the number.
Another newbie, to the Forum. Your posts are moderated. Keeps the spam out of the forum. I wish someone would moderate my phones
Henry
COB Potomac & Northern
Shenandoah Valley
I have a BLI SW1500 to which I want to add ditch lights. The decoder manual indictates there is a function for them. Any idea how I would wire them to the decoder?