Steps to reproduce

1. Place the filled cauldron:

   /setblock ~1 ~ ~ cauldron[level=3]

2. Get dyed armor.

   /give @p leather_chestplate{display:{color:0}} 1

3. Check if there is any item in the chestplate slot.
4. Click on the cauldron with leather chestplate.
   Also, when you wash the armor, there will not be any animation of the hand (before 19w37a).

Code analysis

This is caused by the check if the world is a client or a server (!worldIn.isRemote). Removing it fixes the issue.

if (itemarmor.getArmorMaterial() == ItemArmor.ArmorMaterial.LEATHER && itemarmor.hasColor(itemstack) && !worldIn.isRemote)
{
    itemarmor.removeColor(itemstack);
    //...
    return true;
}