diff --git a/src/libvterm/include/vterm.h b/src/libvterm/include/vterm.h
index 50a840a..f731dcb 100644
--- a/src/libvterm/include/vterm.h
+++ b/src/libvterm/include/vterm.h
@@ -79,8 +79,16 @@
 }
 #endif
 
+/* The ansi_index is used for the lower 16 colors, which can be set to any
+ * color. */
+#define VTERM_ANSI_INDEX_DEFAULT 0	/* color cleared */
+#define VTERM_ANSI_INDEX_MIN 1
+#define VTERM_ANSI_INDEX_MAX 16
+#define VTERM_ANSI_INDEX_NONE 255	/* non-ANSI color, use red/green/blue */
+
 typedef struct {
   uint8_t red, green, blue;
+  uint8_t ansi_index;
 } VTermColor;
 
 typedef enum {