Offset Printing: what is too far off?

We all know that it is technically impossible to have a tolerance of absolute zero between colours in offset-printing. But, lets guess you have white text printed in plane one and a blue text printed on top of it, slighly smaller. Are there any norms, standards etc. in the EU or other countries defining exactly what is to much off? If two dots at exactly the same position in a pdf in different spot colors appear 0.5mm from each other in the print, is that too much off?

For me, it clearly is, i'd expect a tolerance of ~0.1mm, but: is there a norm or anything else on that?