"all "white light" led's emit blue light because they start with a blue emitter which excites a phosphor which in turn emits "white" light".  since the phosphor is not opaque, the led leaks blue light.  tools like flux only change the ratio of blue to red light.  they don't eliminate the blue light.  you can prove this if you use a spectroscope. not sure if this design will provide enough resolution but it is cheap enough to give it a try.http://www.livescience.com/41548-spectroscopy-science-fair-project.html want a cheap solution? get a yellow filter and build a light cage around your light source."