Thanks Noel. I think I'll stay safe and reserve the white caps for my set of Strelets.R "Russian Naval Artillery". But during my research I found this magnificent page:
http://digitalgallery.nypl.org/nypldigital/dgkeysearchresult.cfm?num=560&word=Vinkhuijzen%20Collection%20russia&s=1¬word=&d=&c=&f=&k=0&lWord=&lField=&sScope=&sLevel=&sLabel=&imgs=20&pNum=

100 pages of Russian uniform plates from 1780 to 1900. Enjoy.
Hugh

I have a book here on the Crimean war which is well illustrated and it has paintings by a captain Clifford who was an English officer who was in the Crimea and who was a rather good Painter. In at least two of his sketches their are russian soldiers with White caps. one is very clear and shows ten russian casulties, victims of artillery fire, and the ground is strewn with White caps. In another illustration their is a painting of a Charge by the Heavy brigade by a painter called simpson who was also in the crimea with the army and his paintings are according to the author of the book famed for their accuracy, and 2 Russians in full white uniforms are seen running away. now I know these are drawings and not Photographs but they are by men who actually fought in the war, so they were eyewitnesses and I'd be surprised if they all imagined some Russians wearing white caps.

http://americanmonsters.com/site/wp-content/uploads/2010/04/crimean_war2.png


found this

Thanks very much Noel.