If an LED has a Lens Color, the LED will appear that color when both ON and OFF regardless of the Lens Transparency. If the Lens Color is white or colorless, the LED has potential to emit white, another color, or various colors of light and then return to white or colorless in its OFF state.
(Clear or Diffused) describes “how” light is emitted from an LED. A “Clear” Lens Transparency does not describe a colorless LED in its OFF state, rather “how” the light emits in its ON state.
Clear lenses in their OFF state appear clear regardless of them sometimes having a colored lens, and the inner workings of the LED are usually visible. Clear lenses generally have a more focused beam, and they can provide much more detail or pixilation when in strips or matrixes which can provide more resolution. Since these are not designed to diffuse or scatter the light, they are known to have generally a higher millicandela rating and emit a well-defined circle on a flat surface depending on the surface distance and viewing angle of the LED. In a Clear lens RGB, it is common to see each individual color pixel at short range as opposed to the lens blending each pixel as in a diffused lens.
Diffused lenses in their OFF state appear tainted, foggy, or frosted, and the inner workings of the LED are not usually visible. Diffused lenses when illuminated generally have a lower millicandela rating and often appear warmer and softer to look at since the lens is designed to “diffuse” or scatter the light within the lens making it less directed and having more of an even glow. Diffused lens RGB LEDs blend very well as opposed to Clear lens RGB LEDs where it is common to see each individual pixel especially at short range.
The important thing to note is that although ordering a “Clear” Lens Transparency, the LED can still be “colored” in its OFF state. Per below DigiKey website example, when a “Clear” Lens Transparency is filtered, you will notice most all of the Lens Color options are still available. Therefore, ordering a Clear Lens Transparency doesn’t necessarily give you a “Colorless” Lens Color when the LED is in its OFF state, and of course doesn’t necessarily give you the LED color (such as white) that you need.