You have a few options.
1, prime/basecoat with a lighter colour. A white or grey spray for example.
2, Build up the bright orange starting from a darker tone. ie red or brown base then blend up from that.
3, keep priming with black but if you want to then apply a light colour with poor coverage like yellow/orange first put down a layer of something like astronomicon grey. As a foundation colour it will cover well but is a light colour and so won't bleed through to the orange.
4, keep applying thin layers, it will cover eventually. (colours in the red area of the colour spectrum are infamous for needing a lot of layers for good coverage)
Personally i undercoat with white if i'm going to be painting a lot of lighter colours or want a bright miniature as it's easier to shade down from white than blend up from black.