In RealSense stereo cameras like the D415 and D435, there are two infrared sensors (left and right) and a single RGB sensor.
The discussion below may help you in mapping color to depth. At the bottom of the page,a user shares their own script for how they did it.
Thanks for your advice as always. Actually, it was my misunderstanding that there was an extra color camera. I figured a way to circumvent the necessity of color-depth alignment with D415 (p. 7 on https://realsense.intel.com/wp-content/uploads/sites/63/BKMs-For-Tuning-RealSense_D4xx_Cameras_WP_1.7.pdf )