Abrupt color changes when circle dragged outside

[ghost]

(This issue still exists after the bug fixes on June 8th by myself)

When dragging the circle to the bottom of the color palette, the color changes to almost black. Repeat this process two times, dragging it further and further down to the black area. Then, adjust the hue slider. The colors will not change nicely (it's very discrete) but when the circle is restored to a position in the middle of the color pallette, the problem disappears. The following screen capture may help:

http://cl.ly/2A023B3P2K1j