What color of liquid carbon
Probably white from the heat.
is it very bright gray colorless color. ...
Here is a paper on the phase transitions solid-liquid-gas for carbon.
Liquid carbon is metallic unless the pressure is too low - then it is an insulator.
The metallic form should appear like most metals: silver colored. They don't provide a spectrum in the paper.
And some further discussion here: http://pchemblog.umwblogs.org/2011/10/30/phase-diagram/
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