Clearing Search Criteria clears Check box Button Defaults

Hy.
In a grid app with a search form , I am using a select field MYCOLOR, with check box as a single value selector among three possible values:

Yellow (Y)
Green (G)
Black (B)

with yellow set as default YES and green and black set as defaul NO.

MyColor

The first time the search screen displays it shows yellow set as default which is fine.
But if I click the CLEAN button all the fields are cleared including MYCOLOR and no default color appears, just a blank value (or any value set in the Title attribute)
If I want to put back the yellow color I have to select manually this color from the drop down list.

To me this is confusng because I would expect to press the CLEAN button and see the search form set to the default values , not necesseraly all blanks.

Any idea how to achieve this ?