HK police are spraying protesters with blue-dye water to mark them for arrest

I don't think the presumption of innocence applies like you think it would in this case.

I was thinking if you were getting a lot of false positives, especially with loyalists that could make it a problem

that's providing your expectation of "Justice" being fair...

it would be better if everyone including the cops were all sprayed so the use of blue dye to highlight individuals would be impossible

I was thinking more you could blue up to provide insta-protest-cool.

No I'm the <strike>messiah</strike> protester