Why Yellow
An electronic ballast contains an electronic inverter that generates
power at a frequency that is usually above 20kHz. The power line (or
mains) power comes into the ballast, it is usually converted into DC
power and then the inverter takes the DC power and converts it to power
at a frequency above 20kHz. The main reason for using an electronic
ballast is that fluorescent lamps operate more efficiently (about 10%)
when operated at frequencies above 20kHz than they do at power line
(mains) frequencies. Secondary reasons for using electronic ballasts are
that they are smaller and lighter than electromagnetic ballasts and they
can be easily dimmed.

You'll never get completely rid of the condensation spot.

I have come around halides where the spot does not even move at all.
Ever, no matter what position you burn them.