1). Salicylic acid and derivatives are easily oxidized in air at such a reflux temperature (benzyl alcohol, bp = 205°C).
2). Orange coloration indicates quinone derivatives.
3). Distillation stopping indicates quinone-hydroquinone dimers (quinhydrone derivatives).
So what can be done, is:
Neutralizing the overall obtained product with dilute aqueous NaOH, removing quinone derivatives by solvent extraction, re-reacidification and distillation. But it may not worth the try.
Alternatively, you can repeat the esterification in inert atmosphere (N2) and in presence of a little amount of BHA or BHT. Besides, using TsOH instead of H2SO4 is preferred, as well as using toluene as a solvent to reduce the reaction temperature.
If the latter does not work, select another synthetic method.
You can check the purity of salicylic acid by TLC or even better, by HPLC. If not adequately pure, recrystallize it before the reaction.
Wet Oxidation of Salicylic Acid Solutions, Environmental Science & Technology, 44(22), 8629-8635, (2010)https://pubs.acs.org/doi/abs/10.1021/es1021944
Preparation of Quinhydrone-type Complexes Composed of Quinone Dimer and Trimers, 55th Symposium on Organic Reactions, Session ID: P22, (2005) https://www.jstage.jst.go.jp/article/kisoyuki/55/0/55_0_48/_article
Oxidation of Hydroxy- and Dihydroxybenzoic Acids Under the Udenfriend's Conditions. An HPLC Study, Open Med Chem J., 12, 13-22, (2018) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5815051/