This composite picture is from the public abstract for the first gout study referenced in the Feet Tophi page.
The lower image is a DECT scan which differentiates uric acid deposits, shown here in green. The color is set by the software to provide contrast with natural tissue. Note that, though the patient had not complained of gout pain, uric acid deposits are clearly visible in the toe, foot, and ankle joints. You can find more about this imaging method by searching for DECT in the box above.