blend in(to) (something)
To merge seamlessly and successfully with something. Do you think Sam will be able to blend into the group? He can be pretty standoffish. Be sure to blend in your makeup so that your face isn't two different colors. Don't wear anything too flashy—try to blend into the background.
blend in (to something)
to combine nicely with something; to mix well with something. The oil won't blend into the water very well. It simply won't blend in.
blend (something) into (something else)
and blend (something) into mix something evenly into something else. We should blend the strawberry jam into the peanut butter slowly. You should blend in some more jam.