Weed or grass?
Thank you for your question. Unfortunately I cannot tell from the photo provided.
One weed that grows faster than the normal grass in the lawn and is usually lighter green in color is nutsedge. Here is a fact sheet that describes it and includes a photo- https://www.extension.purdue.edu/extmedia/ay/ay-19-w.pdf
If you would like to bring in a sample to the Sussex County Extension office, please feel free to do so. We are located at 16483 County Seat Highway, Georgetown, DE 19947. The office is open Monday - Friday, 8 a.m. - 4:30 p.m. The sample you bring should include the roots and any seed heads if possible. Grasses can sometimes be difficult and we need to check for rhizomes (underground stems). The seed head can be most helpful for identification - you can leave a space unmowed and let it continue to grow and then bring in a sample. Best regards, Tracy