Crimson Rosellas (Platycercus elegans) should, by definition, be in part crimson-coloured. However, there are two colour varieties that used to be named as separate species – the yellow rosella and the Adelaide rosella.
This particular bird is a yellow Crimson Rosella, where all of the normally crimson feathers are yellow, and this is the form that occurs along parts of the Murray River. All colour varieties have the blue cheek patch though, a distinguishing feature.
Photo taken earlier this week in Echuca, northern Victoria.
Click on the image below to view on iNaturalist.org.