I added an option in svn.
However it may slightly differ from what you expect. The Caret is drawn by Xor (actually NotXor). That means the caret color depends on the background color.
A caret at a selection for example will be half in front of the selection, and half on unselected text. Thus it will have 2 colors.
This behaviour is kept. (you also may need that, if you are on a breakpoint line, that has a different background color.)
You can now set the color for the primary caret, and the color for any 2ndary caret (multi caret mode). If you choose red (rgb #ff0000) then the current background will be bitwise xored with this, and then negated (bitwise not).
So on a white background you will get the color. On a black background you need to set #00ffff to get red.
The background is not necessarily the global background color of the editor, it may be the background color of the current line, the selection, or any other highlight that happens to be there.
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Note: As soon as you use colors (as well as when multicaret is active) the editor draws its own caret, rather than letting the system do this.
This means there may be differences in how the caret displays.