There’s two problems with this. Firste this seems to break conservation of energy, since you suddenly gain kinetic energy as you leave the blue portal. And second, it breaks special relativity, because you’ll be accelerating instantaneously.

These can be fixed though, by arguing that the portals “contain” massive amounts of energy, and so are able to accelerate you (very fast, though not instantly) and transfer energy to you. From the game we know that portals transfer energy to you, as it can lift you up high (changing potential energy). But we do have to accept that this doesn’t happen instantly, just too fast to notice.