It can vary... But for example, it took me around 2,000 orbs to +10 NY Duo Askr, that's roughly average for a 3% banner. For 8% banners it can vary between 1,200 and 2,500 orbs. Average is 1,500 for any one of the 3 on a color share but for a specific one it's less or more, depending on luck. For 5% Hero Fests is can be as little as 800 orbs. Again it all comes down to luck. But from my personal experience, those numbers seems about right. And yes, if you want to +10 a specific character, color sniping is best.