Learn English – Apostrophe use in a title

Firstly, with regard to spelling: "Today it is no longer considered incorrect to use either form (Jones's or Jones') ".

Secondly, ncsu ties together pronunciation and spelling to a limited degree:

Spelling conventions are in some sense an attempt to replicate pronunciation. When style manuals make pronouncements on spelling, they imply that the presence of an extra "s" means that most educated speakers customarily pronounce that sound. The reason that this system cannot simply be reversed to produce pronunciation rules is that style manuals are directed at written language, and they are thus also interested in visual consistency and eliminating visual distractions.

This is in answer to the question:

In American English, how are words that end in "s's" pronounced? For example, if Jones is pronounced as "Jonz," how is Jones's pronounced? And if the above were written to end with the apostrophe (Jones'), is the final "s" silent? Listening to the radio, I notice that many announcers seem to treat the final "s" as silent; but I feel the final "s" should be pronounced as a separate syllable, even in cases where the word is written to end with the apostrophe only.

This article says that you can choose between the addition of the bare apostrophe or the apostrophe s in these cases, but that this then dictates how the resultant should be pronounced. Yet another rule dropped from on high.

This article from Grammar and Style in British English implies that there is a rigorous connection between pronunciation and written form; it recommends that you should decide whether one pronunciation sounds more reasonable, and choose the spelling to correspond as closely as possible. For Jones' / Jones's and Wales' / Wales's, it implies there is no obviously better choice:

Where possessive nouns ending in s make a harsh ziz sound, the option is available of using an apostrophe without an additional s. Thus –

Jones’s house is the one at the end of the street

may instead be written

Jones’ house is the one at the end of the street.

Similarly –

Gareth Edwards was one of Wales’s (or Wales’) finest rugby players.

But the traditional practice is to retain the additional s (Jones's house) unless the resulting pronunciation would be particularly ungainly –

Moses’ tablets / Cervantes’ Don Quixote / Jesus’ disciples

Ultimately, one has to decide whether one is sufficiently pro-'Joneses' to read out Jones' as 'Joneses', etc. In a sense, 'only read the form Jones's as 'Joneses' is prescriptivist. One faces a very similar problem when quoting a passage with alternative spellings one doesn't use, when quoting passages using different spellings, when reading out 'Wagner conducted the Wagner piece' ...

Since "colleagues" is a plural noun and has already been added an "s" to pluralize it you do not add a second "s" to produce the possessive form, only the apostrophe. Something different happens when the plural noun does not finish in "s".(like children --- possessive children's...)