I ask and answer myself, because after seaching I found nobody asked this and I have to solve it myself. And very fortunately, I found the answer and it's quite easy!
First, I try to look at the options for
PlotStyle -like stuffs are its options.
Then I try to dive into the whole blackbox——the FeynArts package's source files. In the very beginning, I copy the diagrams output and query about its Head, and I found it's Graphics (Actually all the
Plots and other graphs are with head "Graphics"). So I guess there should be
Graphics[...,options] in the FeynArts source code. It is by changing Graphics' options that I can achieve my goal.
So I found the 《Graphics.m》 file in the FeynArts folder, which in my case is
C:\Users\19927\AppData\Roaming\Mathematica\Applications\FeynCalc\FeynArts\FeynArts. After testing, there are 2 and only 2
Graphics[...] in it and they indeed control the style of the outcome of
Paint. They are as follows.
The first one is. I add the 415th line of code, to set the painting color to be red. The effect is
, only changing the "PlotLabel".
To see this, you need to quit and reload FeynArts.
The second one is at around line 460. I add the line 460 of code expecting to change sth to blue. The effect is.
So as you see, we find the keys. You can change to any style you want, or suitable for your stylesheet. Btw, I think
Background -> White is much better since we always need to copy the Feynman diagrams to somewhere else.