The sensitivity of the process is determined by the "overlap" of the emission
spectrum of the lamp with the absorption spectrum of the iron or chromium, and
these are also rather broad. That they are sensitive at least in the blue is
evident by the yellow color, and I know from personal measurment that the iron
goes into the near UV and assume that the chromium does too.
The bottom line is that there is nothing to worry about using the "wrong" bulb,
only a possible gain or loss of exposure sensitivity, but that is dependent a
lot on the power radiated by the bulb in the absorption spectrum of the iron or
chromium, how far the bulb is away from the paper, concentration of iron or
chromium on/in the paper, etc.
Let me also add to others, my caution about looking at these UV light sources,
either directly or reflected. They are strong enough to cause itchy eyes (acute
reaction) and with chronic exposure, cataracts. They might not appear intense,
but the eye's sensitivity to blue is very poor, and of course to UV,
non-existent.
Paul Simon