Maybe look at bamboo? I know some types are getting bad press lately but maybe someone can recommend a reputable brand. We have natural hickory in a modern space and love it but you do get that variation so if you don't love that look probably better to avoid it. Hopefully someone can give you some feedback on maple.

White Oak in a natural "clear coat" finish will NOT turn orange. It will fade blond = modern. With your budget, you may have to look at a 'character' grade or Grade #2 in a wid(er) plank. Bamboo can be OK...but you have to go well above your budget to achieve the "does not make you sick" off gassing. Bamboo below $5/sf is NOT something I would work with.

I would look to a 4"-5" solid oak plank quarter sawn for stability with a NATURAL WATER BASED finish that you must specify does NOT TURN ORANGE (does not amber). This is a finish that Europe has been showing for 15-20 years = pale/silvery oak = natural colour of faded oak floors.

Maple can receive a treatment (not cheap but will do the trick) that stops it from turning yellow. This is an application that is applied after the floor is installed but before it is "finished". Look at www.loba-wakol.com. They carry a photo inhibitor in their line up. I believe it only works with floors that yellow...it won't stop other floors from fading or loosing colour.