This isn't the entire reason. Colorado has TABOR that restricts the state from keeping excess money and has to refund it to the people. This usually amounts to like $20 a person.
Secondly the voters consistently vote down public works projects or school funding and the legislature can never come up with a bill everyone can agree on. So there is money there but gets put into pet projects instead of tangible ones.
Lastly you decriminalize marijuana and besides the tax gain from this there would be less incarcerated individuals which also helps the state budget especially if it was legalized.