There is no need for a script. Wikipedia gives you the option via a pop-up no matter the browser.
Even not logged in you can turn it off by:
Hover over any article link.
On the preview, click on the gear icon in the bottom-right corner.
Select "Disable" in the pop-up and then "Save".
AFAIK there isn't a general translation service for translating Wikipedia English articles to other languages, so you have to look at the community area of the desired target language to see if they have instructions to request a translation.
The colours are decided on what kind of artist they have been labeled as in their infobox. Jake Sinclair has been tagged as non_vocal_instrumentalist whereas Andrew McMahon is tagged solo_singer.
Read more about it on the documentation page of the Infobox musical artist