Wiring a dual coloured LED by two different sources

Question

I have a 12V dual colour LED strip that I am trying to power from two different power sources on a motorcycle:

1. Source 1: Daytime running light (Always on)

   This is constantly ON and always on when the motorcycle is on.

2. Source 2: Signal light (intermittent when signals are on).

   This source is only ON (intermittently flashing) when you signal left/right.

The LED strip has 3 wires:

1. Black: positive
2. Red: ground for white LEDs
3. Yellow: ground for yellow LEDs

Questions:

1. How can I wire the two sources so:

   1. Source 1 (daytime): only lights up the white LED
   2. Source 2 (signals): only lights up the yellow

2. How can I make it so the white LED is off while the yellow is on?

Source 1	Source 2	White LED	Yellow LED
ON	OFF	ON	OFF
ON	ON	OFF	ON

Answer 1

Leaving aside legal questions, for a moment...

Since Source1 in your truth table is ON in both positions, the output actually is only controlled by Source2 and we can treat Source1 simply as power. So in this case we can connect Source1 directly to +12V of your LED strip and use Source2 to control yellow/white switching using a relay.

^{simulate this circuit – Schematic created using CircuitLab}

You might want to add a delay circuit so that when the turn signal is off the white light doesn't come on immediately. (that's what I did on my car) This way the turn signal is more visible as it's signalling Yellow/OFF instead of just changing the color Yellow/White.