John,
Based on your scenario, you want to know the color red or white. I am guessing these are NOT separate Items. If not, if I wanted to know the Color, I would create a dimension for Product Color and have values like Red, White, Mixed, etc.... You would set the Dimension Code Mandatory for the Dimension Product Color, on the Revenue Account(s). On each Item, setup the Dimension Product Color, Code Mandatory and leave value Blank so the User can enter the Color on the Sales Order.
Now, if you do have separate Items by Color, then you can setup the Item Dimension value with the correct Color and the User will not need to enter anything.
I hope you follow the setup but here are a few screen shots:


My pic above is using a specific Item to a specific color. If I left value blank, then switch Value Posting to Code Mandatory and user selects in Sales Order. Note that by setting everything up like this any entry involving the Items will require this Dimension to be filled in. If you leave the Item Dimension off, then only Posting to the GL Account example will require the Dimension to be filled in.
Hope this gives you direction and resolution.
Thanks,
Steve