if you just want blue tint, then 6000K will do the job. 10000K will give you purple tint effect. which will be too much and personally I think it is kind ugly.

but serioiusly, I think with projector lens, 4300K does the job nicely.

PS, yes, you can just replace the bulb with 10000K D2S bulb.

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2004 X5 4.4 Sport --- for her
1998 GS400 --- for me
1992 Legend -- totaled
1995 Civic EX -- stolen