Maybe it's just the fact that I'm new to BS4, but I cannot see how to change the color of the carousel page indicators and prev/next arrow controls.
The colors in the starter BS4 template I used are an off-white..and appear to be related entirely to the graphics being used by the controls. There are color palletes for the individual controls but changing them has no effect.
Is there a way, other than creating new graphics, to change the color? The page background color is a light-gray so the controls just kind of blend in. Another possibility would be a second graphic as a border that has a contrasting color.