Here's a better way: Plug image/video texture [Color] to *Separate Color* node, add a *Math Node* and pick 'Divide', plug [Red] to [Value 1] and [Green] to [Value 2], add another *Math Node* and pick 'Greater Than', plug Divide node [Value] to Greater Than [Value], plug Greater Than [Value] to [Alpha] in Principled BSDF