aliased edges on both wheel and slider when surrounding graphics are dark

[chuank]

When using a dark surrounding palette for the color wheel + slider, the edge of both elements show a ring of aliased pixels that seem to be a result of the black value graphic element not completely filling up the underlying colour svg.

To better explain this with images:

Will it make sense to draw this value shading element just a hair larger so the aliased edges can be concealed? Exposing an offset property to adjust this manually will be great, too.

[mxdmly]

Increasing the value of borderWidth has a more obvious effect