I dont know the origin of this yellow rice but I grew up with it. It's the mixed chilli paste, bumbu bali (sambal bali) which produce its distinctive taste. The sambal should be dry not watery. Since my mother did not have a blender, all ingredients were pounded in a mortar. Thus, the pounded dried chillies were quite coarse. The types of fish used are the smaller ones, not the mackerels or red snappers. A condiment is added which is the serunding kelapa, a savory grated coconut, fried til dry enough to not get spoilt easily. We may also add plain boiled egg to the rice. What actually made it aromatic and delicious is because the yellow rice is wrapped in banana leaves, after being cooked in coconut milk with pandan leaves. Just think of nasi lemak.
Nowadays, the nasi kuning is sold in a plastic container, which is more convenient. With this, the nasi kuning has lost its aroma that comes with the banana leaves.