I have just layed a 19 sqm lawn. The turf I recieved does not look as
green or lush as I would have expected.

It's not quite yellow so I'm not sure if this is normal or if it was
staring to dry out to much. I reckon the turf was cut on the monday
and arrived with me on the wednesday, but I bought it online so can't
be sure

The turves felt quite warm when I was laying them, does this mean they
were staring to compost or was it residual heat stored from when they
were lifted? (I would imagine soil would be a good insulator)

I have done all the correct soil prep by raking, stone removal,
fertilising and pre-watering then soaked the turf through after I layed
it so I guess I'll just have to wait and see?

Also, how long will it be before the joins disappear?