How to keep fixed the color of the selected item

1 - Add the attribute android:choiceMode to ListView ,

to allow you to select only one line:

android:choiceMode="singleChoice"

to allow you to select more than one line:

android:choiceMode="multipleChoice"

2 - Add the following attribute to the layout of the list item:

android:background="?android:attr/activatedBackgroundIndicator"

If you want to customize the appearance of the selection, in the res / drawable folder, create a selector

listselector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"
   android:exitFadeDuration="@android:integer/config_mediumAnimTime">

   <item android:drawable="@android:color/holo_green_light" android:state_pressed="true"/>
   <item android:drawable="@android:color/holo_purple" android:state_selected="true"/>
   <item android:drawable="@android:color/holo_purple" android:state_activated="true"/>

</selector>

Change the colors to your liking!

The background attribute of the list item should be declared like this:

android:background="@drawable/listselector"

EDIT after comments

As you are using more than one color for the backgroud of the ListView rows, you need to set a Selector for each of them:

To assign the default background color an Selector item is created without State , this item must be the last of the Selector in>:

listselector_par.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android"
   android:exitFadeDuration="@android:integer/config_mediumAnimTime">

   <item android:drawable="@android:color/holo_green_light" android:state_pressed="true"/>
   <item android:drawable="@android:color/holo_purple" android:state_selected="true"/>
   <item android:drawable="@android:color/holo_purple" android:state_activated="true"/>

    <!-- cor do fundo quando não seleccionada (cor por defeito) -->
    <item android:drawable="@android:color/holo_green_dark"/>
</selector>

Create another Selector , listselector_impar.xml , indicated another color for the background.

Adapter assigns the background its selector as the line is even or odd.

Note:
If you do not like the animation effect, delete the line:

android:exitFadeDuration="@android:integer/config_mediumAnimTime"

or change the value config_mediumAnimTime