One of the unusual properties of the red wavelengths of light - and to a lesser extent, orange wavelengths - is that it does not photograph particularly well; it appears to be much more pale when photographed. If you've ever seen a Ferrari in the flesh, it's surprising how dark the red colour is - it's almost blood red. Ferrari do it deliberately so that the proper rosso corsa colour appears on television.
When McLaren launched, they did so in the studio, which meant that they had a lot of control over the lighting balance, and so they could offset the effects of photography and hence the orange looked quite dark. When the car is out on the circuit, it will most likely look a lot softer and more consistent with the orange-yellow that McLaren officially call "traffic cone yellow".