Todo Q v1.2.3 adds the ability to choose the colors to represent the categories for tasks. Previously only A-D had colors, and they weren't configurable. Now all 6 categories A-F support custom labels and colors.
Also added this release was the ability to adjust the task list font size and icon visibility.
Here's a shot of task list minus the icon and displaying the category color behind each checkbox.
The preferences screen used to adjust the category colors displays the currently selected color for each category.
Colors are selected using the very nice ColorPickerPreference component developed by attenzione.
Todo Q is available for $1.99 on the android market. Give it a try.