Thank you for the additional information.
There are many possible causes of swelling in the feet. It can be due to venous disease, either because of a blood clot in the vein or venous insufficiency. There can be systemic
conditions, such as heart failure, liver or kidney dysfunction, or thyroid
The skin discoloration is a non-specific change in the skin related to the swelling, so does not help to differentiate the underlying cause.
With this amount of swelling of sudden onset, it is better to be seen urgently. Some of the possible causes of swelling should be treated quickly.
Until you are seen, it may help to apply compression of the legs, such as with compression stocking or with an elastic bandage. Continuing the elevation is fine. It may be appropriate to take a higher dose of a diuretic, but it is unclear which diuretic you have been taking.
If I can provide any further information, please let me know. If you would like a phone call and are located in the US, then I can send an offer for service.