Look Ma, Just one WebGL Context

generic webgl

generic webgl no size

red

blue

purple with alpha .5 but alpha:false

green .5 with alpha .5 alpha true (default)

green 1 with alpha .5 premultipliedAlpha: false

preserveDrawingBuffer: true

three.js

WEBGL_draw_buffers

ANGLE_instanced_arrays & OES_vertex_array_object