Problem with Default values with a cascading parameter

I am having a problem where a multi-value Cascading parameter box is not "checking off" all of the options after the "parent" parameter refreshes it if the multi-value parameter includes all of the values.  This looks like it may be a bug or something.  I'm not sure if I can explain this well enough, so I tried to create a simple report that demonstrates this issue on a smaller scale.

I have a table with the following values

ColorName ColorGroup

Blue 1

Red 1

Green 1

Red 2

Green 2

Then I create a parameter from this dataset to display the ColorGroup ( 1 or 2 ) in a drop down box:

Select DISTINCT ColorGroup

From tblColors

Then I create a cascading parameter from the dataset below with the default value set to this query so all results are selected in a multi-value box:

Select ColorName

From tblColors

Where ColorGroup=@colorGroup

Here are the steps to recreate the report:

1.  Select "1" from the first parameter dropdown.  The second parameter is refreshed with Blue, Red, Green - all checked.

2.  Select "2" from the first parameter dropdown.  The second parameter is refreshed with Red, Green - all checked.

3.  Select "1" from the frist parameter dropdown.  The second parameter is refreshed with Blue, Red, Green.  And only Red and Green are checked.

Step 3 is where my actual issue is.  It seems that if the previous results include all the results from the next selection, the multi-value will not check any other ones after the refresh.

Sorry for the long-winded explanation, but I wanted to give as much detail as possible.  I want my multi-value to allways default to all items checked everytime the first parameter changes.

Thank you to anyone who has some time to read this!