If the customer is sensitive to strobing, I honestly just recommend not using LEDs at all just to be safe. My wife gets migraines from strobing lights, and just the intensity of the LED brightness sets her off if in a dark environment. I know I'm not answering the question, and I'm also in the process of experimenting with various LEDs in my own games to see what works best without blowing out my old retinas in my eyes. I'm very interested in what others will suggest here.
Michael