Well, they're different. It's honestly hard to be sure without more information. The darker one is our good friend Pangio semicincita. Going by the extent of the stripes on the lighter fish, they don't seem to go as far down the flanks, so likely a different species. Probably not malayana - bars extend too far down and are too blotchy. Maybe a shelfordii variant. Or even incognito (oh boy these are data deficient). But I'm cutting the speculation and leaving it as 'maybe, but don't sweat it'. I'll explain why.
Unless it's known for certain (if the LFS even bothered), mottled Pangio sp loaches in Singapore often end up sold in mixed-type batches, and that's counting the obvious differences. Different species can cohabit the same river in the wild, and collected as such. Then there's so much individual and regional variation within each species. I can't even discount the possibility of a hybrid, or a species undescribed to science,these guys are not often studied in depth.
You can try counting the bands (still variable), looking at the barbel length (individual can be injured), counting the fin rays ... counting the vertebrae ... but I wouldn't sweat it unless you want to breed them. If you can even get fry. It doesn't matter to kuhlis since they'll all hang out with one another the same.
Oh, and the spots and bars on each fish change a bit with age, size and with injury but it'll keep in the same general shape. Color isn't a good indicator as well since they pale and darken with mood.
Here's more reading material:
https://lkcnhm.nus.edu.sg/app/upload...rbz203-249.pdf
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