The other three are, per Eight Immortal Flavors,:6. Bland, as you found.
7. Fragrant, again as you found. And
8. Golden!"What???" (I hear you saying.) "What's "golden" mean as a flavor?"
"Golden" is that taste that you get in kumquats or in orange rind, the sort of sharp or prickly (my words) or penetrating flavor.
Dave Oesterreich