QCD Feynman rules

Last updated Aug 5, 2023

$$\frac{-i\delta^{ab}}{k^2+i\epsilon}\left(g^{\mu\nu}+(\xi -1)\frac{k^{\mu\nu}}{k^2+i\epsilon}\right)$$ In Feynman gauge $\xi = 1$ so that $$\frac{-i\delta^{ab}}{k^2+i\epsilon}g^{\mu\nu}$$

$$\frac{i\delta^i_j\delta^f_{f^\prime}}{\cancel{p}-m_f+i\epsilon}$$ where the indices $i,j$ are color space matrix indices and $f,f^\prime$ are spinor space matrix indices ??

$$-ig\gamma^\mu \delta^{f^\prime}_f\left(T^a\right)^j_i$$