Fix colors on fabs

AppFab.tsx

@@ -1,15 +1,19 @@
 import { ComponentProps } from "react";
-import { FAB } from "react-native-paper";
+import { FAB, useTheme } from "react-native-paper";
 
 export default function AppFab(props: Partial<ComponentProps<typeof FAB>>) {
+  const { colors } = useTheme();
+
   return (
     <FAB
       icon="plus"
       testID="add"
+      color={colors.background}
       style={{
         position: "absolute",
         right: 20,
         bottom: 20,
+        backgroundColor: colors.primary,
       }}
       {...props}
     />

TimerPage.tsx

@@ -78,7 +78,9 @@ export default function TimerPage() {
           position: "absolute",
           left: 20,
           bottom: 20,
+          backgroundColor: colors.primary,
         }}
+        color={colors.background}
       />
       <AppFab icon="stop" onPress={stop} />
     </>