As you may already know, Don Troiani did a painting entitled "Men of Arkansas" which depicts men of the 9th Arkansas (and possibly some of the 45th Tennessee) being rallied by Gen. Albert Sydney Johnston just before his mortal wounding at Shiloh. It shows some excellent detail regarding uniforms.
As briefly indicated by one of your responders, the 2nd Texas Infantry wore undyed white jackets and trousers at Shiloh. Originally clad in captured federal blue uniforms acquired from Union soldiers surrendering at Texas installations, 2nd Texas Infantry Col. John Creed Moore (before leaving Texas) had sent an agent to New Orleans to requisition gray uniforms for his blue-clad soldiers. When the 2nd Texas arrived in Corinth, Mississippi, just before the Battle of Shiloh, bundles of white wool uniforms were issued to the men of the regiment. As Joe Chance indicates in his fine book on the regiment, with such distinctive uniforms they would soon attract the attention of the Federals at Shiloh. One Federal prisoner referred to the 2nd Texas Infantry as "them hell-cats that went into battle dressed in their grave clothes."