Most metals need a specific etch primer designed to chemically ‘etch’ into the metal, then the paint can hold onto the primer.
An etch primer for titanium might be either non-existent or extremely expensive. This might be one reason why they anodise them, the other reason is that no matter how well you got paint to stick to the stakes, the paint is still sitting ON the stakes and can therefore be scratched off whereas anodising puts the colour IN the metal and can’t really be scratched off.
So buying the anodised ones would possibly be the cheapest option that will work.
Another option is to get some adhesive vinyl as used by sign makers for computer cut lettering. You could wrap the vinyl around that stakes adding of course a tiny bit of weight. The vinyl though not totally durable will probably do better at holding on than a poor paint job. And it could be replaced.
If you want to do this to help you find or see the stakes easily (as opposed to the pose factor), you could just wrap a 1′ or 2′ strip around the top of the stake. This means the vinyl won’t get brutalised so much.
What you call blaze orange (fluorescent) would stand out like dogs ‘globes’ hanging from a rear vision mirror.