cooling system

The temperature sensor may be inaccurate. You can determine this by using a scan tool to read the sensor temperature.

I replaced the temperature sensor with new one's and used a scan tool to read the sensor temperature. The reading is the same i.e Red lamp on at 94 degree c instead of 120 degree c.

I did not advise you to change anything. I advised you to read the temperature using a scan tool.

I have a Hyundai new accent 2008 car, 1.6 l, 4cyl, fwd, manual 1.6l,135000 km ,
Because of overheating before, an over hole maintenance was taken and due to a little deformation in cylinder head, 2 head gasket are installed to compensate the cylinder head thickness after resurface it
The cooling system have 2 indicator lamps one blue for low temp. and the other red for high temp. after some weeks i found the red lamp on in traffic but didn’t in highways
By checking the cooling system
• Replacing thermostat, temperature sensor, radiator cap,
• Cleaning radiator (aluminum type) internally and externally, checking the coolant level regularly is detect no leaks
• Checking the electric fans operation are ok.
• Checking water pump impeller is ok.
• Checking by using another controller
• Checking by using instrument cluster and indicator lights panel controller
• Checking bad gasket and cracked head using block tester and test fluid it found ok.
After that i found the same state red lamp on in traffic but didn’t in highways
Using scan tool which indicate that red lamp is on at 94-96 degree c and radiator fan on at 96-98 degree c and code p0118 ( mean engine coolant temp. circuit high input) so why red lamp

Because you have a problem with the coolant temp sensor circuit. You will have to have the circuit troubleshooted to resolve the P0118.