Hokkien pronunciation of `白头偕老`
nóo vs. ló


These two are both for literary pronunciation. Since 白頭偕老(白头偕老) is a traditional Chinese idiomatic expression (成語 Chengyu), we tend to pronounce it in the literary way. 

The difference between these two might be in the sub-dialect aspect. I'd pronounce it as pe̍h-thâu-kai-ló since it's easier for me to pronounce. But I reckon that pe̍h-thiô-kai-nóo is considered more sophisticated and authentic generally.  


láu vs. lāu


These are indeed two common pronunciations for 老. But I humbly argue that these two are not very likely to be used in this particular context 白頭偕老(白头偕老) (at least in my neighborhood).

I have recorded a clip saying pe̍h-thâu-kai-ló, so you can cross-check with the CD that you mentioned above. Go to pe̍h-thâu-kai-ló if you don't mind my Donald Duck voice.


Hokkien has many sub-dialects, so sometimes people (like myself) might need to be more open-minded about "what is the right way to say a certain word?".


Note and reference:


My parents are from the northern part and the middle part of Taiwan. They use Hokkien(Min Nan) as their first spoken language.
The singer in the music video is from southern part of Taiwan.
I use Mandarin as my first spoken language.