Bulbs not firing as blue (xm20k)

[corpusse]

On my frag tank I run a single 250W SE XM20k bulb. The bulb was really old and looking really white so I replaced it. The new bulb has basically the same colour. It almost looks like when the bulb is fired that it's the purpleish blue then shifts to a whiter colour before it reaches its full brightness.

The ballast I'm using is a coralvue 250w electronic ballast. I should mention some months ago my frag tank cracked and the ballast got wet but not soaked. I didn't use it for a few months as the tank was repaired and when I went to use it again it fired up fine.

On the one hand I don't think it's the bulbs because I did try a new one. On the other hand I don't think it's the ballast because if it got damaged it probably wouldn't work at all and seeing as it does work I find it unlikely it's damaged.

thoughts? thanks