Those tubes are designed to run with anode color, that is what keeps them properly gettered!
With four 4-400 tubes, I doubt you could overdrive them with 100 watts in grounded grid.
40 mA might be a bit low for idling current, but I didn't look at the spec sheets.
Important thing is to watch the grid current and to keep the amp properly loaded.
Thanks a lot for your help.
So, the anodes of the tubes going to orange color is right if I don't exceed 350 Mah of plate current, right?