on the image of him shown in issue 510, page 11 and it would seem he has a combination sharingan/rinnengan eye.
Which, would actually make sense why they've been showing the 10-tails with a combination eye. I know when the other characters think about him, he only has the rinnengan, but in a flash back thinking about a character they only know from legend, it's not necessarily that accurate. Besides, you can make the sharingan appear and go away, so perhaps he did mostly just walk around with the rinnengan.
Which, would actually make sense why they've been showing the 10-tails with a combination eye. I know when the other characters think about him, he only has the rinnengan, but in a flash back thinking about a character they only know from legend, it's not necessarily that accurate. Besides, you can make the sharingan appear and go away, so perhaps he did mostly just walk around with the rinnengan.