Thank you for your response! Ideally we would like to allocate it all to the Colorado spouse. Based on the comment about "allocate the income according to the source of the assets in the accounts" this would be a reasonable method as all assets did technically come from the Colorado income.
If all of the unearned income is allocated to one spouse, is there any reporting requirement for the other (New York) state tax return? In this particular situation, there is no New York tax liability as all pay for the New York resident is military and the New York spouse is considered a non-resident of New York (domiciled in New York but does not maintain a permanent place of abode there, does not live there, and maintains a home in a different state).
