LED light sensor device

I am looking to make a device that I can take to a location and put over an existing, properly operating light and get the kelvins from the existing light.

I am hoping I can do this with both fluorescent and Metal Halide as this project unfolds.

any idea where to start ?

This would be for use in projects that would be to repair or replace lights with lights that are close in color.

and get the kelvins from the existing light.

Kelvin is a temperature scale. Are you seriously trying to measure the temperature of a light bulb?

Yes, you can do this. You just need a very accurate RGB sensor, and you have to calibrate it.

PaulS: Kelvin is a temperature scale. Are you seriously trying to measure the temperature of a light bulb?

lamps are measured in kelvin. a typical dayling is 41 kelvin, a more yellow warm white will be closer to 32 kelvin. I don't make up the names....

http://www.3drender.com/glossary/colortemp.htm

it gets more of a science, color renedering. LED's can offer lots of light, but you cannot tell red from coral as the color rendering is horrible with LED's.