Answer: Unfortunately, you will not be able to plant this outside and expect it to survive, it is just not cold hardy enough to handle your weather.
It may be that the room is too warm, although you did well to manage to get it to set buds so that may not be the (only) cause. You need cool nights and cool days, with maybe 10 degrees difference between them. Usually camellias are grown in a relatively cold greenhouse rather than in the home because our homes are simply too warm.
If the discoloration is beginning at the tips of the petals and the flowers are balled, I would suspect lack of moisture or uneven moisture levels changing from very dry to very wet for example. Although you do not want to overwater your camellia, the soil should still be well moistened when you do water, then kept slightly damp.
There may be some sort of soil or nutrient imbalance. For example, a long term lack of phosphorus can sometimes cause camellia buds to drop without fully opening. Make sure you are using a good quality, complete fertilizer that also includes trace elements. Supplying phosphorus would not work immediately, but you would see results next year.
Camellias can suffer a fungal problem called petal blight that causes the buds or blooms to discolor and fail to open fully. The discoloration would begin at the center. This may be the early stages of that. It lives over from season to season on mulch, debris and stems, and thrives in humid conditions or wet weather. If you think this is it, you might consult with your local professional nursery staff and see if there is a fungicide you could try on an indoor camellia. Also change the surface layer of soil and clean up and remove all fallen foliage, petals, faded blooms and so on immediately to try to limit reinfection. And, increase air circulation to try to inhibit fungal infection.
Finally, depending on the specific variety you are growing, some of the japnicas are quite susceptible to this bud/flower problem. So it may be due to that rather than anything in particular you are doing or not doing.
I hope this helps.
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