Way to confirm dichromate ion presence where other ions are messing with the color
The best reagent for detecting Cr(VI) in aqueous solution is the diphenylcarbazide, which produces a red color in presence of Cr(VI). The sensibility limit is as low as 0.2 ppm Cr(VI). This method has been developed one hundred years ago. See 
1) M. A. Moulin, Dosage du chrome, Bull. Soc. chip. 31, 295 (1904).
2) H. Crossley, Diphenylcarbazide. An indicator for the titration of iron with dichromate. Analyst 61, 164 (1936).

The reaction with alcohols to produce aldehyde and acids does work. But it is not very sensitive. It needs at least some millimoles of chromate to be detected. The reaction with diphenylcarbazice is about 1'000'000 times more sensitive.