New source found from dndbeyond.com

ddb_main/components/Button/Button.tsx

@@ -1,5 +1,6 @@
 import clsx from "clsx";
-import { FC } from "react";
+import Color from "color";
+import { CSSProperties, FC } from "react";
 
 import {
   Button as TtuiButton,
@@ -33,7 +34,14 @@ export const Button: FC<ButtonProps> = ({
   const isCustomSize = size === "xx-small";
   const isCustomVariant = variant === "builder" || variant === "builder-text";
   const isCustomColor = color === "builder-green";
-  const { isDarkMode } = useCharacterTheme();
+  const { isDarkMode, themeColor } = useCharacterTheme();
+  let overrideStyles: CSSProperties = {};
+  if (isDarkMode && themed && variant === "solid" && size === "xx-small") {
+    overrideStyles = {
+      // Determine if the theme color is darker or lighter
+      color: Color(themeColor).isDark() ? "" : "black",
+    };
+  }
 
   return (
     <TtuiButton
@@ -53,6 +61,7 @@ export const Button: FC<ButtonProps> = ({
       variant={!isCustomVariant ? variant : undefined}
       // Children are included in props
       color={!isCustomColor ? color : undefined}
+      style={overrideStyles}
       {...props}
     />
   );