at the beginning of every diary is this paragraph:

 

 

 

"Once you've spoken to one of these people, your Diary won't look any different. But the first time you complete a task in the diary, the entry will turn yellow (showing that you've started the Diary, similar to the quest list.) If you click on the Diary, it pulls up a parchment list in your main game window. You can scroll through it to see the complete list of tasks."

 

 

 

In actuality, the area of the diary (karamja, varrok, ect.) turns from red to yellow when you talk to one of the people to begin the achievement diary. Once this happens you can begin the diary tasks

Fixed now, thanks.