Please upload pics of teeth preparation. otherwise its very difficult to say anything. in your case its re veneering , so little more preparation is must.
I'm impressed with your photoshop skills, however, you already have a straight tooth.... its just rotated. Rotate it in the right position, it will last longer and look better than any veneer. Consult an orthodontist for your options.
Looks like the "yellow" is the underlying tooth structure. The tooth underneath has not been fully covered. Since you chose a very higher value (brighter) in the final restoration, the opaqueness contrasts against the base tooth shade. Breaking contact between the teeth, to wrap the restoration...
