Problems already

I'm a newbie so bare with me. I bought my new macbook yesterday and it was going fine until i tried to plug my external hard drive. I forgot what it said about the hd but after that it turned all my folders blue and it takes forever to open them. My Macintosh hd cant open unless i open it up in finder. please help i would like to correct this problem because its making me uneasy. Thank you in advance

Spotlight (the service that searches your hard drive) is likely indexing your external hard drive. You can view its progress by clicking the magnifying glass in the upper right corner of the menu bar.

Let it go and it will eventually return to normal speed once it finishes building indexes.

not only does it do it to my external hard drive it does it to my internal hard drives and all its folders

Yup, it will. Just let it finish up and you'll be good to go. Now, if you've forcibly shut the machine down while it was busy doing its thing, you might have prolonged it or caused a problem with the disk structure.