Re-add hard coded color to FAB

This is a bit more cheerful

lib/screens/measurement_entries_screen.dart

@@ -21,6 +21,7 @@ import 'package:flutter_gen/gen_l10n/app_localizations.dart';
 import 'package:provider/provider.dart';
 import 'package:wger/providers/measurement.dart';
 import 'package:wger/screens/form_screen.dart';
+import 'package:wger/theme/theme.dart';
 import 'package:wger/widgets/measurements/entries.dart';
 import 'package:wger/widgets/measurements/forms.dart';
 
@@ -72,7 +73,7 @@ class MeasurementEntriesScreen extends StatelessWidget {
                             TextButton(
                               child: Text(
                                 AppLocalizations.of(context).delete,
-                                style: TextStyle(color: Theme.of(context).errorColor),
+                                style: TextStyle(color: Theme.of(context).colorScheme.error),
                               ),
                               onPressed: () {
                                 // Confirmed, delete the workout
@@ -115,7 +116,11 @@ class MeasurementEntriesScreen extends StatelessWidget {
         ],
       ),
       floatingActionButton: FloatingActionButton(
-        child: const Icon(Icons.add),
+        backgroundColor: wgerSecondaryColor,
+        child: const Icon(
+          Icons.add,
+          color: Colors.white,
+        ),
         onPressed: () async {
           Navigator.pushNamed(
             context,