With some plant varieties, like Chameleon ZZ or some types of Arrowhead Vine, the new growth is naturally lighter in color and it deepens as it ages. On these varieties, it is normal. On other varieties, it is not normal, but may not be anything to worry about.
One common occurrence is that a new leaf will begin to unfurl while in the darkness of the box while it’s being shipped to you. In this case, there’s not light to activate all the chlorophyll in the leaves. It’s easy to fix this: Once you unpack your plants and give them good light, the chlorophyll will develop in several days to a couple of weeks (it varies by plant species) and they’ll take on their natural color again.
If your new plant does have pale new growth when you take it out of the box, avoid placing your plant in direct sunlight. Because there’s not as much chlorophyll in the leaves, they’re more susceptible to sunburn.