Unhardcode textbox colors in textbox arguments

There's a few places where textboxes are constructed through code, but
they pass in the color's RGB values in manually. This commit
unhardcodes most of them them, replacing them with a color lookup.

The ones that weren't changed are special cases, like `175, 174, 174`.

desktop_version/src/Graphics.h

@@ -69,28 +69,29 @@ public:
 
     void createtextboxreal(
         const std::string& t,
-        int xp,
-        int yp,
-        int r,
-        int g,
-        int b,
+        int xp, int yp,
+        int r, int g, int b,
         bool flipme
     );
     void createtextbox(
         const std::string& t,
-        int xp,
-        int yp,
-        int r,
-        int g,
-        int b
+        int xp, int yp,
+        SDL_Color color
+    );
+    void createtextbox(
+        const std::string& t,
+        int xp, int yp,
+        int r, int g, int b
     );
     void createtextboxflipme(
         const std::string& t,
-        int xp,
-        int yp,
-        int r,
-        int g,
-        int b
+        int xp, int yp,
+        SDL_Color color
+    );
+    void createtextboxflipme(
+        const std::string& t,
+        int xp, int yp,
+        int r, int g, int b
     );
 
     void textboxcenterx(void);