That's basically what you have with most LED plant lights - red + blue ~ magenta. But just red and blue don't really quite cover ALL the needs for most plants. Plants to not live by photosynthesis alone.

Two things come to mind:

1) Plants use all spectra of light; green gets a bad rap because most of it is not used.

2) Magenta is a combo of violet (about 400 nm) and red (about 640 nm). But that excludes the blues, orange, lots of the red, all wavelengths that play a vital role in contributing to growing mature fruit or plants.

Two things are important if one wants to grow plants from seeds to harvest: spectrum and intensity. Some 5000K CFL bulbs have a near perfect spectrum but they do not have the intensity, unless one wants to 400 watts to grow a tomato plant. Others (LEDs, HID) have the intensity but often lack the complete spectrum needed.

The futuristic LED panel will have violet, 2-3 shades of blue, green, yellow, orange and 2-3 shades of reds in their array. Or, they will be totally white. I have a couple of low power, white LEDs that when the light is reflected off a prism show the entire gamut of visible light.

Mike