I've been playing with my Fiesta last month, changing all the interior lights in order to make them multicolor, as in the US Fiesta.
I added LED strips in the front and rear footwell,
I changed the LEDs of the lightguide on the dashboard and on the cupholder;
I changed the LEDs of the dome lights, to make them RGB, adding a dome light with leds also on the rear.
All the LEDs are independently controlled by groups (one group is the footwells, the second group are the LEDs on the dashboard and in the cupholder, and the last group are the dome lights), so that each group can be color matched (since they're different types of LEDs) to the others and independently set for the brightness.
The electronics controlling the lights has been completely home made, it is connected to the BCM, so it senses when the vehicle is commanding the ambient lights and the dome lights. In this way I can turn on and off the ambient lights using the settings of the radio, as well as the lights switch to white and max brightness as I open a door or turn off the engine.
I use a rotary switch close to the USB port to change color and brightness.
Here's the result, hope you like it!