"Colorado already proved that with the tax revenue they brought in from legalized marijuana"
Colorado probably got significantly increased business from being the first, surrounded by neighbours where it is still illegal. They probably even have increased secondary trade from people travelling in to get marijuana and then buying other stuff. Also, there's probably the effect of the novelty. I'm not saying there isn't a permanent increase, but it will be less if Nebraska and Oklahoma also legalise it.
"Probably even have increased secondary trade" doesn't even begin to cover it. My wife works in ophthalmology and she has four patients who have moved to colorado just because of pot. That's likewise cited as a primary reason that housing prices have increased recently. I find it hard to believe that people would uproot their lives just for weed, but it appears to be happening.
Colorado is making an estimated $1M/day in taxes on pot and that's probably significantly lower than the actual revenue, since because there are virtually no banks (one credit union) that'll deal with marijuana dispensaries, it's a cash-only business so the businesses could in theory only report as much business as they wish, and pocket the rest. If/when more financial institutions start dealing with them, and people feel they can use credit cards to pay for pot, the tax revenues are likely to increase.
It's also not clear that the novelty is outweighed by the convenience. There are a lot of people who didn't use pot previously because it was just a hassle to get and there was a bit of risk involved. The people I know who are long-term smokers have stayed with their black-market dealers because they know it's safe and it's cheaper. But people who want to use it occasionally, or don't know/want to deal with black-market stuff, is apparently a huge market. They may overwhelm the local novelty effect.