Expert witness discovery is governed by Colorado’s Rules of Civil Procedure, Rule 26. COLO. REV. STAT. ANN. § 4-26 (West 2017). The rule requires disclosure of the fee arrangement that the expert witness and the party have agreed upon for the expert providing testimony. Id. The court has allowed discovery into the portions of an expert’s income that are from sources other than the expert’s ordinary income to show bias. Donelson v. Fritz, 70 P.3d 539 (Colo. App. 2002).