HOW DO THEY LOOK?

In reality "WHITE" LEDs aren't perfectly white. Since there is an internal tiny blue light source,
and due to mechanical placement tolerances, many of these white LEDs have a very light blue
tint to their appearance (some blue light sneaks out without hitting the white florescent paint).
At low LED current levels, the white appearance is much like a modern halogen type lamp.
In comparison to a white piece of paper, the output is about 95% white light and 5% very light blue.
The best appearance comparison we can make is…they look just like those unusually bright
headlights on the 1997 & 1998 Lincoln Mark 8's and other luxury cars and SUVs. When used
on model trains…they look great when compared to the cheap, ugly yellow LEDs. Over a wide
range of input voltages, their light output will be almost constant.

COMMON WHITE LED QUESTION: HOW DO THEY WORK?

There are 2 types of White LEDs available for Optics & Lighting Displays…

White LED Type 1: (Small Scale Railway sells this type of white LED.)

In reality this type is like the florescent lamp tubes commonly used in homes and businesses.
Inside there is a tiny little blue LED inside a cup shaped cavity that is coated with white florescent
paint. The blue light activates the white phosphor within the paint to produce the "white" light we
perceive. (The common florescent tubes use blue light created by an electrical current
passing through a mercury vapor.)

White LED Type 2:

In reality this type is made up of 3 to 4 different colored LEDs that are pulsed randomly. These
will provide near perfect white light, and can be tuned to provide any color in the visible spectrum
(even a rainbow). Due to the manufacturing complexity of this type and extremely high cost,
nobody in the world buys and uses this type of LED technology for model/hobby products.
They exist mostly as lab samples, but are being developed to improve their cost and reliability.
Since this type of "LED" can actually be tuned to provide any color in the visible spectrum,
expect the see items like Christmas tree/ornamental light strings in the next 10 to 15 years
using this technology (10 years ago blue and white LEDs didn't exist).