I'm assuming you mean that there used to be stripes and now the stripes are receding and it is just yellow on top of his head. This happens because your bird is getting older. This is normal so there is no problem. If this is not what you were asking about, then I need more information. :)
Where does it turn red? If it is the cere (nose) then this means the bird is not in a breeding mood (both genders). my budgie was doing this when he was a few months old. if the face is turning red where the feathers are maybe he has a skin condition and you may need to take him to an avian vet
mabey there sick or mabey they have a swolen head.
Just don't think about being red and be mature
No its not in their diet
yes!
that's normal
Turning red around girls is a natural reaction. Some girls see it as awfully cute.
If by face, you mean the cere (area above the beak, surrounding the nostrils), then no it just means that your female is not in breeding condition. I think parakeets more naturally breed in the spring, so if you wrote this anytime recently (ie winter), this is normal.
Parakeets do not become pregnant, they lay eggs. Females have a pink or tan color nostril band.
you could text, email, message(facebook/msn etc.) him :]
Yeah, although maybe not in all people. You know your face is turning red when all the blood goes up into your head, you feel a nerve climax in your brain, your nerves are just buzzling. That is true anger...
try by not being scared , ask him if he likes you
I don't completely understand but if you mean the thing above the beak is turning pink it means it's a girl.
When i am embarrassed my face turns BRIGHT red and it is horrible! .. so what i do is when something embarrassing happens i try to think about something else that wont make my face red, such as the place you like to be the most, or a funny joke. Just remember if something embarrassing happens people will eventually forget about it!.. dont worry! hope i helped (: !