Please be aware that if you dye denim or colored patterned items that have not soaked into the fibers properly, the color may fade if you soak them together.
When it comes to colored patterned items, it all depends on how well the dye sticks to the fibers, so when making a decision, try dissolving a small amount of Rinenna in water in an inconspicuous area and tapping it to see if the color fades.
Many denim fabrics and red and white hats are relatively susceptible to color transfer.