Last Wednesday on GH, Sam and Danny visited Monica for Thanksgiving. During these scenes, Sam was wearing a purple plaid shirt. Sam's worn this shirt before, but I haven't been able to locate it. I found a few similar options below. If you recognized Sam's shirt, please let us know who designed it in the comments. For details on Sam's tie-waist navy trousers, check out this previous post.
Sam Morgan's Purple Plaid Shirt.
Here are some alternative purple plaid shirts for a look similar to Sam's: