I've looked at different walkthroughs for this part. One says use the lure in the upper right corner while another says use the one in the upper left corner. I've tried all of them but all I ever get is green salmon. How do I get the orange one I need?

There is book in the hut telling you that they are particular about color of their prey. This fish likes green frogs and prefers shaded areas downstream of waterfalls. With this it should be easy for you to pick the correct spot out of the four and to catch the fish. Don't forget to take the basket that's in the hut with you and place it near Kate else Yuki will eat it. ;-)

Way to not answer the question...

It's the upper right lure BUT you also need to cast not in front of you, but to the right.