xenon headlight

[Dygital]

Hey gang,

I have OEM Xenons on my '05 X5, and when I had started the car up in my garage the other day, I had noticed that the right headlight is shining with a more pinkish/purplish color rather than the normal light blue/green, which is what the left one is still shining. looking at the headlights from the outside, both look fine, no dimming, the difference is only noticeable when shining both headlights at a wall at a close distance. Has anyone experienced this ever? is this a sign that I will need to replace the bulb soon? If so, any idea how much they cost?

Thanks!