Just wanted to make a small change on the correct answer at the top. Make a custom XML file for your spinner item inside the layout directory.
spinner_style.xml:
Give your customized color and size to text in this file.
<?xml version="1.0" encoding="utf-8"?>
<TextView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="?android:attr/spinnerItemStyle"
android:singleLine="true"
android:ellipsize="marquee"
android:textAlignment="inherit"
android:textSize="15sp"
android:textColor="#FF0000"
android:padding="5dp"
/>
Now use this file to show your spinner items inside your java file:
ArrayAdapter<String> adapter = new ArrayAdapter<>(this,R.layout.spinner_style,list);
adapter.setDropDownViewResource(R.layout.spinner_style);