how to get just particular single pixel color

[pknmax]

Hello,
Is it possible to render just single pixel which returns the color of each single ray from different colmap camera positions using depth/diff-gaussian-rasterization?

I am interested in getting final color at particular location for different view directions, by providing 3DGS pointcloud, location of target pixel for tracking in first fully rasterized image using first colmap camera pose from colmap pose sequence or 3D location in scene (how to find it?), and colmap camera poses.
Can you please guide me to achieve this?