mnist_caffe example : prototxt

[Source82]

Hi,
Please excuse my ignorance. If I was to use the mnist_caffe example for my custom resnet model, at what point will I pass the prototxt file. Obviously the model is passed at line 49 of the code
armnn::INetworkPtr network = parser->CreateNetworkFromBinaryFile("model/lenet_iter_9000.caffemodel",
{ }, // input taken from file if empty
{ "prob" }); // output node

what i don't understand is where to specify the prototxt file

Will the mnist_caffe example also work for color image - I presume the data part of my prototxt file specifies the channels. Am I right?