There are a ton of beautiful organic bedding options at Pottery Barn Kids.

PotteryBarn Kids has some patterned and colorful organic sheet sets. Not sure about the dyes used, but they are organic cotton.

There are lots of online stores that sell organic fabric in different colors and patterns ; you can always get them made into sheets or do it yourself if you are handy with a sewing machine. This way you not only know what you are getting but is also more economical. A word of caution about pottery barn organics: I once read in one of their catalogs that a particular bedsheet had 5% organic fiber and was easy care finish !! Doesnot make sense. I once wrote to them about their fabrics on a kids bucket and this is what they had to say:

"Thank you for contacting Pottery Barn Kids.

Please know there is a difference between flame resistant and flame retardant. All of our fabrics are flame resistant and meet all flammability requirements. None of our products use chemical flame-retardants.
The government has set standards for appropriate rate of burn for various materials. Products described as flame resistant fall within an acceptable range for the rate of burn of the material used.
If we may be of any further assistance, please contact us via email. Alternately, you may contact our Customer Service Department directly at 1(800) 290-8181 from 6:00am to 11:00pm (CST), seven days a week."

Hello,

I just ordered beautiful twin sheets for my little girl from Cotton Monkey www.cottonmonkey.com

On their website, they show only crib sheet sizes, however Michelle was kind enough to custom make twin bedding for me. They have beautiful prints and patterns, are 100% organic, start to finish, and unlike pottery barn's "organic sheets", they add no chemical "finishes" to their products.

Check them out, you'll be glad you did!

One more thing: I did hours of research trying to find truly organic kids sheets with great prints and colors...I could find several options without any patterns or prints, however, Cotton Monkey was the only one with these great and gorgeous prints and patterns! They will soon add twin sheets to their line, but until they officially do, if you contact Michelle I'm sure she'll make whatever you need!

Thanks, Stacy