well since this one is made as a exhibit it has to be more attractive.if i use IR people will not see any thing attractive.normally people visiting exhibitions dont know technical stuff like IR obstecle detection etc.for them what they see is what they understand.
this is how my robot became most attractive robot in the exhibtion.
(small kids and grown ups loved to see it working evan though its not a big deal to us.)
another reason is white light reflects on most surfaces except black,so should work on most of surfaces without tuning.
