Partial appearance update for one layer. Every field is optional; only the
fields present are applied, each through the same code path the Layers
panel's own control uses. colormap: null returns to direct colour;
layerOrder: null releases an explicit order.
Partial appearance update for one layer. Every field is optional; only the fields present are applied, each through the same code path the Layers panel's own control uses.
colormap: nullreturns to direct colour;layerOrder: nullreleases an explicit order.