Could you solve the following question ?

A SiO2 layer is thermally grown at 1145 C using a 20-25-30 min dry-wet-dry O2 oxidation cycle. Upon pulling this (100) wafer from the furnace, the oxide color is observed to be royal blue. Is this the expected color? If not, suggest what might have gone wrong in the experiment. (It is possible to quickly check the thickness of SiO2 on silicon by observing its color under daylight