Fill both saucepans halfway with water and bring to a boil.
Peel just the yams, chop them into bite sized pieces and add to one of the boiling pots of water. Leave the skin on the red potatoes, chop into bite sizes pieces and add to the second pot of boiling water.
Heat a skillet on medium and cook the bacon until crispy, then set aside to cool. Cook the yams and potatoes are JUST fork tender, about 10 minutes, then strain.
In a large mixing bowl whisk the red wine vinegar, dijon, salt and pepper. Add the strained yams and potatoes while still hot and gently toss until the liquid has been fully absorbed. Lay evenly on the baking sheets to cool.
When the yams and potatoes are completely cool, prep the rest of the ingredients. Dice up the green onion, chop the celery and crumble the bacon.
In the large bowl combine the mayo and sour cream, then mix in the celery and green onion. Gently toss the yams, red potatoes and bacon into the sauce.
Enjoy!