Im trying to do research on the topic, but have only found information that doesnt *confirm* what was used. Like a manual for how to use the FN FAL in a museum dated 1960, this confirms that manuals were needed for it but not that the FN FAL was actually *the* standard issue firearm (though I do suspect it is that or the m16. maybe m1/2 carbine or m14 though I think thats unlikely?) it would be even better if someone can find jungle camouflage uniforms.
You would be correct with your assumption of the FAL being the standard service rifle of the Dutch military. The Netherlands had used American-supplied M1 Garands in the aftermath of WW2 up until 1961, at which point they had selected the FN FAL to replace it.
The Dutch had tested the FAL as early as 1954 and, like many customers, they opted for a number of unique features on their guns. They used the same stamped steel handguard and bipod pioneered on the German G1 models and more commonly seen on the Austrian Stg 58s, and muzzle device was a 22mm grenade-launcher/flash hider combination that was unique to Dutch rifles. They'd be the only operator to opt for a fully enclosed front sight and they were the first customer to use a non-adjustable rear sight (as seen on the 50.63 "Para" models). In addition to the standard service rifle models of the FAL, the Dutch would also adopt the 50.41/42 FALO, which was a heavy-barreled FAL designed for use as a squad automatic weapon.
M16 variants wouldn't be available until sometime later by the Dutch - the AR-15 was a very new product in 1961 and was struggling to gain traction domestically in the US, and the Dutch wouldn't replace their FALs until 1995. There was a company in the Netherlands - Artillerie-Inrichtingen - that was producing several models of AR-10 (the gun that the AR-15 was scaled down from), and they had even succeeded in getting a small order from the Dutch military for rifles to evaluate. But the Dutch, like nearly every other nation to evaluate the AR-10, would opt for something else.