I'm doing a search on this topic of "How can I select my color instead of the default automatic color selection?" I ran across this post which has no reply. So I'm guessing that you can't. I'm guessing that when you go to Source Data click on Add Series you have no choice but Patterns Automatic Line Color. If that's the case, and I'm guessing correctly then it would be great if an expert in Excel would verify that such is the case, and I can stop wasting time looking elsewhere for the answer.
Here's my post on the topic
Here's what I'm doing
I need all the series to be one color, and going back to format all 29 lines so they are black gets to be tedious.
A macro that says, "Select (Chart1) Select (All Series) Select (Color) Select (Black) Select (OK)" would be just the ticket.