You have options:
1. Use a variegated in the top and red in the bobbin. Some of the variegated threads have really short transitions which means you would have an even distribution of visible versus blended appearance.
2. Use a a monopoly in the top and red in the bobbin. Adjust the tension so the red won't pop to the top.
3. Use a neutral in the top which would show on all parts (more so on the dark) and a red in the bottom.
4. Select threads to match the color in each section and change the thread accordingly. I'd still use red in the bobbin.
Have fun.