I've been putting together a box recently and came across an interesting piece of quartersawn sycamore:
I decided to use it for the center section of my box's lid, but I wanted the color change to be centered horizontally on the piece. Here's how I did it.
First, I used masking tape to define a straight, repeatable line that I wanted to center on:
Then, I took it to the table saw and used a known good piece of plywood as a straight edge against my tape:
Butt the straight edge up against your fence:
I don't know why I didn't take a photo of this, but with the straight edge butted up against the fence, butt your miter gauge up against your workpiece and set it to match the angle. Then make your cut on one end (this cut ended up being something like 87*):
Go ahead and flip the workpiece and square up the other end.
Reset your miter gauge to 90*. Take your newly "90 degrees to the tape mark" end and put it on the miter gauge. If you look closely at the image, you can see the shadow of my fence riding just along the edge of the tape. So the tape is parallel to the fence. Good.
Now make a rip cut using the miter gauge.
Flip the board and do a regular rip cut against the fence to get your 4th parallel/perpendicular side and you're done!
Now please... somebody tell me there's an easier way! This is the first time I've done anything like this and it seemed very very fiddly to get it all right.