Scotts has the same warning on their label for Step 1. All you can do now is wait. Hopefully, the lawn will green up within a short time. If not, you may have to re-seed after the Princep washes through.
I guess thats it like you said. I read and read the directions but I sure missed something? Hers some directions I went by;
Precautions: On newly sprigged turfgrass, hybrid bermudagrass, nondormant bermudagrass or nondormant zoysiagrass, temporary slowing of growth and yellowing may occur following application.
To avoid turf injury, (1) Use only on turfgrass reasonably free of infestations of insects, nematodes,
and diseases. (2) Do not use on golf greens. (3) Do not use north of NC (except in the VA Coastal
Plains) or on soils with a pH above 7.8. (4) Do not use on muck or alkaline soils. (5) Do not apply
over the rooting area of trees or ornamentals not listed on this label. (6) Do not seed or overseed
with desirable turfgrass within 4 months before or 6 months after treatment. (7) Do not apply this
product to newly seeded grasses until they have overwintered and have a well-developed rhizome
system. (8) Do not exceed 2 qt/A of Princep Liquid within 12 months of seeding grasses. (9) Do not
exceed 2 lb ai/A (2 qt/A of Princep Liquid) per application. (10) Do not exceed 3 qt/A Princep Liquid
(3 lb ai/A) per calendar year. (11) Maximum of 2 applications per year