I don't think you can apply conditional formatting to a check box, so how
about a text box that simulates the check box?

Delete the check box from the report.

Replace it with a text box, and set these properties:
   Control Source    NameOfYourYesNoField
   Name                 NameOfYourYesNoField
   Font Name          Wingdings
   Width                0.18 in
   Format                            {see below}

Type these 3 characters in the Format property:
- Hold down Alt, and type 0168 on the numeric keypad. Release Alt.
- Type Backslash
- Hold down Alt, and type 0254 on the numeric keypad. Release Alt.

Now apply conditional formatting. The text box has the value True or False.

Duplicate this text box for your other fields as well.

The trick relies on the fact that Access uses 0 for False, and -1 for True.
The Format expression tells it to use different formatting for a negative
number. The actual formatting expressions are the Wingdings characters that
look like unchecked and checked boxes. If you have the Character Map
installed (Windows applet), use it to find the characters.

It's a useful trick, giving you not only conditional formatting and coloured
check boxes, but resizeable check boxes (just change the font size), blanks
for False, and unboxed check marks for True.