The orange helmet is a model you do not have, if you want to play as a orange helmet then you need to pick a model you don't have (in some sense)
Step 1 : Open your console by pressing ~
Step 2 : type model along with anything after that so say... Model none
Step 3 : ???
Step 4 : Profit
You're now the orange helmet, you'll see yourself as an orange helmet as long as you don't have an actual model named none, if you do then you might as well type something like model hdagioah and it'll work as well.