Thanks for the hint, Tim. I’m still not clear what to write though to apply these ideas to produce an image with two channels that range from black for 0 to the specified colors for each channel.
It seems like I need to use channelview or colorview, but how do I apply the palette to the grayscale images? I guess I would need something like the color_me function from this post? But it doesn’t accept my ch1_grad as a second argument, so I still can’t tell how to get my colors applied.