Poker Stars $0.25/$0.50 No Limit Hold'em - 9 players
The Official 2+2 Hand Converter By DeucesCracked Poker Videos

UTG+2: $101.30 14/12 (658)
MP1: $14.10
MP2: $50.75
CO: $40.75
BTN: $70.75 20/15 (107)
Hero (SB): $50.25
BB: $50.00
UTG: $98.50 17/13 (160)
UTG+1: $77.85

Pre Flop: ($0.75) Hero is SB with K:heart: K:spade:
UTG raises to $1.50, 1 fold, UTG+2 calls $1.50, 3 folds, BTN calls $1.50, Hero raises to $7.50

Too hot? Too cold? Just right? Any villain reads that might make you adjust the size?

I wouldn't have made it any more than $6 myself, honestly.  This just doesn't look like it's going to get paid off by a lot of worse hands -- maybe queens, jacks, and AK.

Well, you have to consider what the bet sizing projects in terms of your willingness to commit X amount of dollars on the flop.  Even to fish, a raise of "a lot" is going to lead to the assumption that you're going to bet "a lot more" on the flop.  I'm not sure how often you're going to find people 4-betting into this reraise with worse hands or simply overcalling with some weak hand, but $6 (4x the bet) can look like more of a squeeze since it does give better pot odds to hands like TT and 99 while building the pot in the same aggressive fashion that $7.50 would but also saving you money when you do make an attempt at a bluff here.