Ok, I need help!

I have these two tops (dresses? onesies?) from baby gap and I have no idea what to put on bottom. White tights underneath the onesie? gray leggings over the onesie? black leggings over the onesie?

Please comment with what you'd put on bottom for each!!

Teal:
http://www.gap.com/browse/product.do?cid=65210&vid=1&pid=915121002

Lavender:
http://www.gap.com/browse/product.do?cid=65210&vid=1&pid=915125002

The bottoms I have available are:
black leggings
red leggings
heather gray leggings
white tights
black tights