This would somewhat depend on time of year. The GJT departure is not until 410P, so maybe 5P counting late time. So certainly once daylight savings time is over there won't be much daylight. DEN departure is in the morning (1030ish), I have not been on the DEN-GJT stretch, but we found the GJT to SLC route quite scenic, at least until sunset. We went August 2019.