You can tint Tru-Oil, but you're better served dying the wood rather than the top coats. Here's why... If you dye the wood, you can highlight the figuring or grain pattern using multiple colors, techniques (dye, then sand back), and products (BLO for 'pop'). After these processes, apply the TO for an opaque, durable finish.
If you tint the TO, you lose the ability to highlight the natural beauty of the wood for the following reasons: TO does not soak into the wood beyond the first application. TO is basically BLO with hardeners added. Subsequent applications of TO build layer upon layer with each new application. If you tint the TO, you will be adding a new 'dark' layer to your project with each application. The more layers you apply, the less opaque your project becomes-- you lose some visual of the wood grain with each application of tinted TO.
Not my first choice, but if you must.... Oil based paints in TUBE FORM work well. You can find them at art supply stores.