Several companies including Apple are attempting to produce red, blue, and green Micro-LEDs for high-resolution displays. So far, little progress has been made. Micro-LEDs seem to promise high resolution with a lower cost than OLED displays. However, many technical roadblocks remain. Companies are finding it difficult to produce RGB (red, blue, and green emitters together) micro-LEDs.
According to a Digitimes article, companies have not successfully arrayed RGB micro-LEDs and attached them to a substrate. One proposed alternative is to use quantum dot materials with a blue chip to produce the red, blue, and green colors. However, the quantum dots degrade in just a few hundred hours.
So, despite their promise, micro-LED-based displays are still not feasible with current technology.