What are the rules or practice in writing or pronouncing “á” in Ulster Irish ? . I’ve noticed a lot of words where the síneadh fada is ignored in pronunciation. Words such as:
coláiste is pronounced colaiste without the á. The same with arán, iománaíocht, galánta. Some areas seem to maintain the fada. Is this dialectical within the province? or are there any rules?.

the general rule in Northern Donegal is this:

á is pronounced like a short [a] when it is unstressed. It doesn’t mean the sìneadh fada is ignored, because unstressed “a” (without accent, then) isn’t pronounced [a], but rather [É™] when broad and [ɪ] when slender. For instance if it were “colaiste” it would be pronounced “ko-lish-cheh”, but it is pronounced “ko-lash-cheh”.

á is pronounced [É›:] (a long eh-sound, roughly) when it is stressed.

aràn : ah-rahn
iomànaìocht : oh-mah-nee-arrt
galànta: gaw-lahn-tuh (“gaw” is short)

àit: aytch
bàn: bwayn
clàr : clayr
(I wrote “ay” for a long eh-sound, I dunno how to write it in this English-like transcription)

Btw in the title of you message you wrote “Gaeilge Ulaidh” but it should be “Gaeilge Uladh” (or in Ulster Irish, “Gaeilg Uladh”, pronounced “Gaeilic Ulù”), since “Ulaidh” is nominative and “Uladh” is genitive 🙂