Add readable pastel tile backgrounds and refresh setup documentation

tests/test_tile_palette.cpp

@@ -0,0 +1,9 @@
+#include "components/smart_display/tile_palette.h"
+#include <cassert>
+int main() {
+  assert(tile_palette::color("auto")==0);
+  assert(tile_palette::color("")==0);
+  assert(tile_palette::color("unknown-future-choice")==0);
+  assert(tile_palette::color("red")!=0);
+  assert(tile_palette::color("green")!=tile_palette::color("red"));
+}