Comment by adrian_b

When you use any kind of filter for a lamp, that stops a part of the light produced by the lamp, the part that has an undesired color.

So, at the same electric power consumption you have less light, or you can compensate by using a more powerful lamp, to get the same amount of light even with a filter. In both cases the energy efficiency becomes worse, i.e. the expenses for electric power are greater per output light.

On the other hand, when the manufacturer of the lamp controls inside the lamp the conversion of the light produced by the LED through fluorescence into the light that exits the lamp, there are chances to obtain a desired color and a certain shape of the emission spectrum by wasting less light than with external filters.

Filtering can correct a lamp color that is not the color that you want, but it cannot fill gaps in the emission spectrum of the lamp.

Cheap white LED lamps not only may have a too bluish color (or in some cases a too yellowish color), but their emission spectra may have gaps, so if a natural object from the environment happens to have a color that falls in a gap of the LED lamp spectrum, it will appear much darker than in daylight. This can cause orientation problems or difficulties in identifying certain things.

Where LEDs are used for signalling, not for lighting, so pure colors are desirable, much less problems exist, so e.g. the replacement in the red or yellow signal lights of cars, of the old incandescent lamps with color filters, with monochromatic LEDs without color filters, has posed no difficulties.