Fix truncation warning color_picker.c->draw_screen

Change-Id: I72f16163684aba6c9c3fcf4ade6f2906d80b3899
diff --git a/apps/gui/color_picker.c b/apps/gui/color_picker.c
index a66b131..03096e5 100644
--- a/apps/gui/color_picker.c
+++ b/apps/gui/color_picker.c
@@ -259,9 +259,9 @@
         display->putsxy(text_x, text_top, buf);
         /* Draw color value */
         if (display->depth >= 24)
-            snprintf(buf, 4, "%03d", rgb->rgb_val[i]);
+            snprintf(buf, 4, "%03d", rgb->rgb_val[i] & 0xFF);
         else
-            snprintf(buf, 3, "%02d", rgb->rgb_val[i]);
+            snprintf(buf, 3, "%02d", rgb->rgb_val[i] & 0x3F);
         vp.flags |= VP_FLAG_ALIGN_RIGHT;
         display->putsxy(text_x, text_top, buf);