I have not tried all Iris colors, but I thought they all reduced? Even raku does. I think you'll have the best luck searching for each color as QuiteCuntrary said.
Also have you looked at glasscolor.com? They show most colors reduced and not, such as iris violet
http://www.glasscolor.com/products/d...cID=23&pID=283
Iris Orange 'Raku" as said will reduce to silver, but most strike it to get colors, I believe that's the only one that is different in that aspect.
http://www.glasscolor.com/products/d...D=120&pID=1637
There is a huge thread in gallery (i think?) on working raku, you'll find it by searching, it's like a million pages lol