Hello John, Would you happen to know what stain you had before?
It is difficult the match the older stain even if the stains are the same because the older deck is now seasoned and the stain looks different on it. I would suggest you sand and re stain both areas to have a more cohesive look.
I still have five gallons of the stain we used on the house. It is a few years old but I have kept it rotated and in a dark cool place. I tried a small area on the old ceday and it is a good match. I am concerned that on New cedar it won't look the same. I think pressure washing or sanding might do the trick.
John, Yes you are right that it may not look the same on the new cedar but will start to look fine as it ages, might now still match with the older stain though. Re stain is the best you can do for both areas. Good Luck!
It is difficult the match the older stain even if the stains are the same because the older deck is now seasoned and the stain looks different on it. I would suggest you sand and re stain both areas to have a more cohesive look.