If the Colts do want to trade-up and take Dee Milliner in the first round of the 2013 NFL Draft, they'd have to give up a lot.
If we use SB Nation writer Matthew Fairburn's recent mock draft as a guide, Milliner is probably a Top 10 pick. Personally, I don't see him getting out of the Top 8, but we'll be a bit looney and say he is at least a Top 12 guy.
I like using DraftCountdown.com's trade value chart whenever I'm looking to gauge the value of picks. If Indianapolis wanted to trade into the Top 12 (let's say a trade with San Diego at No. 11), they'd have to surrender their No. 24 overall pick, their third round pick (84th overall), and most likely a second round pick in next year's draft.
Sorry, I don't see it, especially with other glaring needs that must be addressed in this draft, such as pass rusher, wide receiver, and the offensive line.
The only reason I can think of for why Ryan Grigson would want a closer look at Milliner is if they are hearing "chatter" that he'll drop like a stone on the first day of the draft. IF Milliner falls, and IF he is still sitting there at pick No. 22 to the Rams, then MAYBE that's the time to trade-up. I say this assuming that the Vikings will gleefully snatch him up at pick No. 23, right before the Colts' turn to select.
Still, that's a lot of "ifs" and at least one "maybe" if you are counting at home.