I'm afraid the color won't tell you anything about the bulbs you've got there. As both HIDs and halogens may be white, blue, yellowish. What will make difference is the bulb itself. Or the bulb size, if you happen to find it out. See the picture, here's what is different
Now, here are the headlights that will work on the 530i
with factory halogens. For the HIDs, the whole headlight setup would be different, as well as the bulbs and the way they operate.
As for the bulb sizes, the halogen bulbs are marked as H1, H7, H4, 9004, 9007 etc. The HIDs installed by the factory feature bulb sizes like D2S, D2H, D2R....
One more idea to check whether the 530i is halogen or xenon is to turn on lights and see if they will flicker once right away, you know, like HIDs usually do. Those are the things that come to my mind. Hope this helps, man!