I have slate grey with a delivery date of 22-24 and still preparing for shipment, with no evidence of it through reference searches with UPS and Fedex. So I don't think the color has anything to do with it. Probably more with where in the country you're located.
I didn't nevessarily mean if you got a different color yours should have shipped already, I meant more if you ordered a silver one then it definitely hasn't shipped yet.
Yours could possibly just be in the second wave of slate gray iPads due to ship today too. And the first batch of silver ones also hasn't gone out yet