There are 3 options to change the indicators colors:
1. When you first apply them.
2. Once applied, left-click over the indicator to highlight it, then right-click and chose the option Edit Series, the window to change the colors will open.
3. Left-click over the indicator to highlight it, then on the left bottom of the chart, chose the new color/shape
How do I know the indicator is highlighted?
When you left-click over the indicator, black boxes will appear indicating that it has been highlighted.