It is a pretty female. I see that you have your birds enjoying some time outdoors, please make sure that they are never left unattended while out, it would only take a second for a predator to knock over the cage and perhaps grab one of the budgies.
I got the yellow one about a month ago, it could just about fly slightly then and became pretty tame easily but ever since being placed in the cage with the other birds, it seems reluctant stepping up or allowing me near it unless its hungry. Is that normal or did I put it in with the others too soon?
The reason your "newest" budgie is reluctant to come to your hand is because it really wasn't "tamed" previously.
It was submissive simply because it was unable to fly so it couldn't really get away from you.
Now that it can, it is showing that it isn't comfortable with you touching it.
You should never try to touch your budgie or force it to be held when it isn't comfortable doing so.
Taming and Bonding is all about helping your budgie learn to trust you and it takes a great deal of time and patience on your part.
You should never grab your budgies or force them to be touched.
To bond with your budgie, you need to build their trust in you.
They will have to learn over time that you will not hurt them, grab them and try to force them to allow you to hold them.
As you have mixed genders in the same cage, you need to be doing everything necessary to prevent breeding.
I also suggest you change the paper out on the cage more frequently. You have allowed quite a build up of droppings.
The paper should be changed daily at a minimum.
Good hygiene is important for healthy birds.
How many budgies do you have in total?
How large is the cage in which you are housing them? Length, Width and Height
It was ok with stepping up or coming to me even when it started to fly normally. It still does when it feels like it but certainly less than it used to. It even flies over to me at times. I never touch or force them unless they seem happy to let me do so. I will take on board the advice regarding the toys and changing newspaper, just haven't been able to as frequently as I would like lately. The cage is large, they can fly from one end to the other and to/from perches easily. I'd say it was approx 80x50x60cm. I don't intend to breed them atm as we don't have space for more birds/cages. There are four in total, two were taken on as a last resort/exceptional circumstances as the owner was unable to look after them. Is the yellow one a male? Thank you
From what I can see of the cere, the yellow does look to be male.
However, for a definitive answer, it would be best to try to get a full frontal picture of the cere taken in natural light and post it.
Are all of the other budgies female? I see two females in the pictures you posted but don't see the third budgie.
Rearranging their cage frequently and limiting the light they get to 8 hours a day will help tremendously to discourage breeding
Please be sure you never put a nest box or anything that could be used as a nesting site in their cage.
When they come into condition, limit the amount of protein in their diet at that time.
Would anyone be able to tell me what gender and mutation this one is and if its still a baby as its confusing due to having the iris showing as greyish but still has the head bars? belongs to my friend.