Cr film sputtering

Hi, I am having issues with magnetron sputtering of Cr. The chamber and the film seems to have coloration after depositing the film at 3 mTorr
and a DC power of 50-100 W. Since the Cr film should look like a nomal metal (no color), I am looking to find solution to this issue. Also, can anybody help me in understanding the drift in the manometer pressure reading when the plasma is turned on for deposition? I would appreciate any input. thanks.
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