[ic] little loop question

[Twentys]

I've got a little problem:
ex.
I've this products

SKU       COLOR
01	blu
02	yellow
03	red
04	blu

I want a select box with the color, so I've done

  <select name=search1>
<option value="">All colors</option>
              
                       [loop option=color search="
                        ra=yes
                        fi=products
                        ml=50
                        tf=color
                  "]
             
                  <option value="[loop-data products color]"> [loop-data products color]</option>
                  [/loop]
  </select>     

But so I have something like this parameters in my select box
blu
yellow
red
blu

It write 2 times blu....
How can I have
blu
yellow
red

without repeat blu?
Thanks to everyone (sorry for my english)
Rolando