The first LED lights due to their red colour were used as indicators in various electronic consumer applications, typically to show that they power was on.

When yellow and green LED lights were developed there was now the opportunity to use LED lamps in traffic lights. With the recent advent of high power LED lights we are seeing an increasing use in channel lighting (signage), traffic lights, automotive lights, street lights, emergency lighting, aviation lighting, residential and commercial down lights and light bulbs, LED replacement of fluorescent T12, T8 and T5 tubes, LED track lighting, pool LED lighting, strip LED lighting for cabinet and bulkhead highlights, garden LED lighting and even LED lighting for growing plants.

As mentioned it wasn't until the development of blue high power LEDs in 1994 that the production of white or warm white light with LEDs were possible. This was initially through the mixture of red green and blue LEDs to make white light or light of different colours known as the RGB system, which is still used in Strip LED lighting.

With improvements in technology yellow phosphers were used on or near the blue or near-ultraviolet LED light to enable the production of a whiter or yellow light. Interestingly, if one looks at the warmer LED colours the colour of the LED has a deeper yellow reflecting the phosphor content, whereas the whiter LEDs have a pailer yellow colour. 

References:

The long history of light-emitting diodes. Electronic Products (Garden City, New York), v 53, n 9, September 2011