Hi John,
You are not doing anything 'wrong' as such. Perhaps you could adjust your exposure times slightly higher - but it wouldn's make a huge difference.
Fundamentally, your EL panel is NOT producing 'white' light, at least not as far as your imager is concerned. But that alone, isn't really too much of an issue either. It would seem to be 'white enough' to do the job.
And the 'orange cast'? I always used Background Color Correction to get the 'neutral grey' that I wanted from my Master Image (after Crop and DBE, and before Color Calibration).
After that, it was a long way diwn my list of noise removal and range compression steps before I ever considered trying to enhance the colours that I knew would still be lurking somewhere in the depths of my image.
However, if you just want a rought idea of what your image contains, then just remember to unlink the sliders in the STF window before applying an STF to your image.
Hope this helps.
