いざ訪ねては来たものの

いざ訪ねては来たものの特に話すことも思いつかず、僕はなんとか会話を繋ごうとする。

Hi. What does いざ mean here?
By the way, does the は in red used for emphasis?
Thank you.

人を誘ったり、張り切って事を始めようとする時に発する語。さあ。どれ。

いざ has a few meanings, one which can be used as an exhortative and one which can refer with energy/effort/etc. Basically it kind of emphasizes the following action/occurrence and makes it feel like it's a big deal (or a bigger deal than it would be without the いざ). You'll also see the expression いざという時, which is often translated into English with idioms like "when push comes to shove" or "when all the chips are down", but is literally "at the time that can be described as 「いざ」", i.e. a time that's important for whatever reason.

The は is typical contrastive は (which I guess can be considered "emphatic" in a sense). The speaker came to the place in question, at least, but he didn't know what to do or say once he got there.

Thank you. I see.