Using Illustrator CC 2015.
I created a circle shape and the I select the fill color to be a bright red Red:255 G:0 B:0.
Problem is that the shown color of the circle is not red but a kind of orange.
I made sure that the circle:
- has Opacity: 100%
- the layer is at the very top of all other layers
- No masks
The Color Mode of the document is RGB