This one's an easy
for me.
The Machado one is borderline as well but I'll wait on that one.
Chaps isn't playing this year, is he? So his contract is over. Or your re-sign him based on last year's performance which doesn't make a whole lot of sense seeing as he'll be pretty well 2 years older than last year's performance stats. For that reason I'd say Hand>Chapman.
Witt Jr. is what, a top-10 baseball prospect? That plus VVM and Olivares isn't even close to comparing with Gray for me. Especially given P-contracts versus an already "vet" contract.
For me I see COL trading away 2 of it's top value players on the roster (Hays and now Witt Jr.) in exchange for a couple "big" name veterans past their best years both fantasy wise and real life wise, and a middle of the pack SP in Gray (for our league with fewer teams than normal leagues on here I'd say he's just middle of the pack, nothing fancy for a 28-year old).