First some background.
You can get a fairly uniform look once everything settles but it's important to realize that there are hundreds, or thousands of cultivars of seed that have slight differences in appearance. Everything from color, texture, growth rate can vary as can other factors such as resistance to drought and disease.
There are a few main families of commercially sold grass seed which most people shopping for lawn seed will have heard of. Kentucky Bluegrass, Tall Fescue, Fine Fescue, Perennial Ryegrass, Bermuda, St Augustine, Zoysia, etc. These are the main species of grass and what you'll normally find in big letters on the front of the grass seed package.
Not all seed bags contain a single type of grass seed. Some contain a mix. For example a mix of tall fescue and kentucky bluegrass.
On the back of the bag you will find a certification label that shows the exact cultivars of grass seed in the mix.
To get a decent match you need to identify the type of grass that is currently in your lawn. You won't be able to know the exact cultivars unless you know what the grass had been seeded with but figuring out if it's tall fescue, bluegrass, bermuda, etc is possible.
When you go to get sod buy the same type of grass that is growing in your yard. Best way to accomplish that is cut out a section of turn from your lawn and bring it to the sod farm for comparison and advice.