Kant had forever hidden the ding-an-sich (things in themselves) behind the phenomenal veil; that Wittgenstein was obviously familiar with Kants philosophy is suggested by TLP 2.0251
Space, time and colour are the forms of objects
which appears to allude to, whilst overturning, Kants notion how space and time are the forms by which objects can be experienced; he is affirming - instead, via Spinoza, that objects themselves have 'extension' in time and in space; and that objects have 'colour'.
Husserls phenomenological project was to overcome the Kantian distinction as explained by his famous quote
to go back to the things themselves
This recalls TLP 2.1511
thus the picture is linked with reality; it reaches out to it.
It's by reaching out to reality that Wittgenstein establishes the truth and falsity of propositions; recall analytic propositions are true by virtue of their form; and then note TLP 2.224 which has
It cannot be discovered from the picture alone whether it is true or false
He also summarily dismisses a priori truths in the following proposition:
There is no picture that is a priori true
Thus Wittgenstein grounds truth in correspondance, in relations between the picture I have of the worlds and it's states of affairs, and the world itself, as he affirms in TLP2.233
In order to discover whether the picture is true or false we must compare it to reality
and this can only be established by going right up to the world and establishing just what the states of affairs actually are.