too low contrast in checkboxes of update manager

In Karmic Koala default color theme, update manager's checkboxes are dark. As the "checked" marks are dark also, it is really hard to tell whether a checkbox is checked or not.

How to reproduce :
1) Have karmic koala not up-to-date, with two updates to be installed and the default color theme
2) Open the update manager
3) Look at the checkboxes. The checkbox of the highlighted update has good colors, but all the other have a dark mark on a dark background. I could not tell these were checked until I paid really, really close attention.

Expected behaviour : it ishould be instantly clear whether a box is checked or not, through good contrast between the mark and the box.