I have a tiny spot of something orange on my new t-shirt that is resisting everything. I'm about to try Milton (sterilising fluid) which usually deals with even the worst stains, although there is a risk of fading the colour too. This is a white t-shirt with a blue pattern and the stain is on a white part, so I'm hopeful...
If the orange spot could possibly be from a tomato based sauce, such as a Bolognese etc. try leaving the t-shirt on a windowsill in the sun, ( if it ever shines again), for 4-5 hours and it'll probably disappear as if by magic.
I discovered this some time ago when DS left a stained top on the conservatory table waiting for me to rescue it. When I got round to it, the stain wasn't there ! Apparently strong sunlight disappears tomato based stains without any effort from us