You're using a number selection only. Where as #dedede which is a valid hex colour will never show because it's not numbers.. Kind of hard to explain how hexadecimal works...

Sorry if you already know and this is condecending.. :p Denary is 0-9, Hex is 0-15 per unit. When you get past 9, it goes from A onwards. i.e denary 10 = hex A.