[Ruby], 139 bytes

def f c;c=~/#(.)?(.)?(.)?(.)?(.)?(.)?/;$6?c:'#'+($5?$1+$2+$3+$4+$5*2:$4?$1+$4+$2+$4+$3+$4:$3?$1*2+$2*2+$3*2:$2?($1+$2)*3:$1?$1*6:"0"*6);end

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Ruby, 127 bytes

c=~/#(.)?(.)?(.)?(.)?(.)?(.)?/
$6?c:'#'+($5?$1+$2+$3+$4+$5*2:$4?$1+$4+$2+$4+$3+$4:$3?$1*2+$2*2+$3*2:$2?($1+$2)*3:$1?$1*6:"0"*6)

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Ruby, 139 bytes

def f c;c=~/#(.)?(.)?(.)?(.)?(.)?(.)?/;$6?c:'#'+($5?$1+$2+$3+$4+$5*2:$4?$1+$4+$2+$4+$3+$4:$3?$1*2+$2*2+$3*2:$2?($1+$2)*3:$1?$1*6:"0"*6);end

[Try it online!][TIO-jmif7t6q]

[TIO-jmif7t6q]: https://tio.run/##KypNqvz/PyU1TSFNIdk62bZOX1lDT9MeG9a3VjGzT7ZSV1bX1lAxtVcx1FYx0lYx1lYx0VYx1TKyUjEBi5mAhU0gMlYqxkBBLaCAEYgwBikzstcA69XUMrZSMQRJm1kpGShpmWlap@al/C8oADoFaAkXlBGKYIUhMcOR2REonEhUXpT6fwA "Ruby – Try It Online"22+$32:$2?($1+$2)3:$1?$16:"0"*6);end

[Ruby], 139 bytes

def f c;c=~/#(.)?(.)?(.)?(.)?(.)?(.)?/;$6?c:'#'+($5?$1+$2+$3+$4+$5*2:$4?$1+$4+$2+$4+$3+$4:$3?$1*2+$2*2+$3*2:$2?($1+$2)*3:$1?$1*6:"0"*6);end

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