Yellowish tinge during titration of oxalic acid with potassium permanganate
Without knowing the concentrations of the involved substances and the values of some other parameters, we can only guess what has happened during your experiment.

The intended analytical reaction is the reduction of purple permanganate to colourless $\ce{Mn^2+}$:

$$\ce{MnO4- + 8H+ + 5e- &lt;=&gt; Mn^2+ + 4H2O}$$

If you add the permanganate solution too quickly, the reduction may be incomplete because not enough reducing agent (here: oxalic acid) or acid $(\ce{H+})$ is available in the reaction zone:

$$\ce{MnO4- + 4H+ + 3e- &lt;=&gt; MnO2 + 2H2O}$$

The observed colour may be caused by a cloud of finely dispersed particles of dark brown manganese(IV) oxide $(\ce{MnO2})$, which dissolves when the solution is well mixed again so that the intended reaction continues.

The same reaction may occur when you don’t add enough sulfuric acid, since $\ce{H+}$ is consumed during the reaction (8 mol $\ce{H+}$ per 1 mol $\ce{MnO4-}$).