Blender Git Loki

Annotations: Change default color for new annotation layers

Although we've had a default color for new Grease Pencil layers for
years, hardly anyone ever changed the default color from the old
default of black. This commit changes this default to match the
color used in the annotation pencil icons, giving it a stronger
connection to the tool, and giving users a better default color
that will make the new strokes actually visible with the default
theme.