I wish I had good news for you but I don't. New growth in the spring for poison ivy can be green or red. I have a couple pictures in the Pictures section - look for the link for pictures of poison ivy primarily in the spring. Here is a direct link to one of the early plants I saw this year: early poison ivy. As you can see in that picture, the leaves are very red and small. This plant was hiding in some grass about 4" tall. I've seen new growth on poison to be red or green (the literature tends to point to one color or the other).

The urushiol oil is not actually on the exterior of the leaf but is contained in the leaves, stem, vine, and roots. Unfortunately, the leaf is quite fragile so it is likely that Fido trouncing through the plants would break a leaf or two and end up with urushiol oil on the coat. If your dog went swimming afterwards, its likely that the oil will be washed off the coat. We send our dog swimming after he's been in a patch and have had success (i.e. no known rash from him after a swim).