mismatching panels on wooden floor

Hello All!
I have just sanded the floors on my 1930s house and have varnished them with the 1st coat of clear satin Varnish. I had to replace 3 boards of wood and have noticed that they appear much lighter than the rest of the boards.
I tried staining them which made them match and then I Varnished them and the match had gone!
Any ideas on how to improve this before I go to the second coat? Also - how many coats should I apply? Is 2 okay?
Regards
Nick

New wood will always look cleaner than old wood,floor belt sander can do it sometimes but hard work or put the new wood on out of sight area then swap it with the old wood for matching.

As you've already varnished the new boards this is a little late...but...

I stained my new boards - to match boards laid in 1910 - with coffee grounds - several coats - and then varnished. Only I know where they are now!

Hi
Thanks so much! In fact what I did was to Varnish the 3 boards with antique pine Varnish and then Varnish clear varnish on top. Presto! They match perfectly!