1. The VISA functions and VIs will be useful for communicating with the LED controller.
2. The strings you may need to write are determined by the command set for the controller. You must get that information from the manufacturer of the controller. I have no idea what command tells the light to be Blue for example.
If the sequence will always be white, red, blue, green, and off, then you only need to set the timing. I would use an array of numbers (ms) with an element for each color. Then the program would be implemented as a loop with autoindexing over the time array.
I would probaly do something more complicated, on the assumption that as soon as this works, someone will want to do something different, such as change the order of the colors or mix multiple colors. I would use a Producer/Consumer architecture with user inputs handled by the Producer and a state machine in the Consumer to manage the lights. There are templates and examples of these architetctures with all recent versions of LV.
Lynn