Silver dapple is black with at least one copy of silver. Bay with silver is known as a silver bay but some still call it a silver dapple. Silver does not show on a red base so either parent could carry silver and you wouldn’t know without testing. Dapple grey is just a stage in the greying process. Grey is a pigment disease that causes the progressive loss of pigment on any base color. A parent MUST have grey or silver for it to pass on. On a red based horse grey would be obvious. Silver would not.
Agree with Elizabeth. What can be confusing is when silver is on bay, the horse can look like a lovely dark chestnut with a light mane and tail. Their points, which on a bay would be black, but on a silver bay can be very light gray or smudged looking, so some folks may not notice them.