First of all you need to create a class which extends RecyclerView.ItemDecoration :

public class SimpleBlueDivider extends RecyclerView.ItemDecoration {
private Drawable mDivider;

public SimpleBlueDivider(Context context) {
    mDivider = context.getResources().getDrawable(R.drawable.divider_blue);
}

@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    //divider padding give some padding whatever u want or disable
    int left =parent.getPaddingLeft()+80;
    int right = parent.getWidth() - parent.getPaddingRight()-30;

    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount; i++) {
        View child = parent.getChildAt(i);

        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();

        int top = child.getBottom() + params.bottomMargin;
        int bottom = top + mDivider.getIntrinsicHeight();

        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}

}

Add divider_blue.xml to your drawable folder :

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="<http://schemas.android.com/apk/res/android>" android:shape="rectangle">
<size android:width="1dp" android:height="4dp" />
<solid android:color="#AA123456" />
</shape>

Then use it like :

recyclerView.addItemDecoration(new SimpleBlueDivider(context));

The result will be like :

http://i.stack.imgur.com/j70CI.png

This image is just an example how dividers working , if you want to follow Material Design specs when adding dividers please take a look at this link : dividers and thanks @Brenden Kromhout by providing link .