well, this is the code to populate the color text box:
document.WADAInsertForm.color.value = document.WADAInsertForm.ProductName[document.WADAInsertForm.ProductName.selectedIndex].text
this says to set the value of the color text field to use the label from the select list. the label in the select list is what you see when you make a selection.
a simple example would be:
<option value="1">One</option>
in this example, the label, or what the user sees when the make a selection is "One"
document.WADAInsertForm.ProductName[document.WADAInsertForm.ProductName.selectedIndex].text
would return this displayed label "One"
in your code, the options are being populated by a recordset:
<option value="<?php echo $row_items['consignor_id']?>",><?php echo $row_items['item_id']?></option>
it is using the Item_ID for the label, so that is what is being passed to the color. if you want to pass something else for the color, you need to use a different recordset column for the label.