The worst water I've had in my life in Europe (taste- and looks-like) was a green liquid in parts of Wiesbaden, Germany, back in the 1960s. This is obviously no longer the case there or anywhere else on the continent. One hears a lot of urban myths about chemicals to combat rust, salts of all kinds, odd colour and, of course, lots and lots of pathogens. I've often wondered whether these "rumours" are not spread by local and multinational water bottling companies. Other than a potential etiologic agent for urolithiasis (for which there are indications that environmental factors play a role, which cannot be quantified and neither specified for an individual person affected), drinking tap water anywhere in Europe is generally considered to be safe. My own rule (have had several kidney stones so far) is if it tastes good, drink it. Avoid, though, at all costs non-bottled water, even in minimal quantities, in places that are known to suffer from non-optimal public health. One can start from
here to find facts on drinking water worldwide.