I am moving states from WA to CO. CO has a state income tax, WA does not.

I'm trying to figure out at what point I become a CO resident and therefore liable for state income tax. I am staying with the same employer.
My WA house sale closes on May 13th. I will be leaving WA on April 15th and driving to CO arriving April 19th. I will be staying in temporary housing starting April 19th
I currently have an office and a phone number BOTH in WA and CO. On April 15th I will only have an office in CO.

When will I be considered a CO resident for tax purposes?

1) When I sell my primary residence in WA, May 13th?
2) When I move into the temporary housing, April 19th?
3) When I leave WA, April 15th?
4) When my company changes my office address to CO?
5) Other?

Another question: I will be receiving a significant amount of income ($50k) on around May 17th. Any legal and ethnical way I can have this as WA source income and therefore not subject to CO state tax? The income is reimbursement for my house selling costs from my employer

Thanks in advance!