Scots pine wood represents one of the important tree species used by the wood processing industry in many countries for both interior and exterior applications. It is well known that thermal treatment alters the color of wood. To protect wood from outdoor environmental conditions, certain chemicals are applied to its surface. These protective chemicals also influence the color of thermally treated wood. In this study, the color-altering effect of picture varnish (refined linseed oil), commonly used as a protective chemical in the field of painting, was investigated on both thermally treated and untreated wood materials. In this study, Scots pine (Pinus sylvestris L.) wood samples were subjected to thermal treatment at 212°C for 2 h. Following this, varnish made from refined linseed oil was applied to these samples with different treatments and controls. Color and whiteness index (WI*) values were analyzed on the resulting 4 different materials, and the results were compared among them. Significant variance analyses were obtained for the factors of heat treatment, picture varnish application, and their interactions on WI* (║ and ⊥), a*, L*, ho, b*, and C* values. In the non-heat-treated samples, the application of varnish resulted in reductions in WI* values in both directions and in L* values, while increases were observed in ho, b*, C*, and a* values. Additionally, the application of varnish on the heat-treated samples resulted in an increase in a* values,while reductions were observed in WI* values in both directions, as well as in ho, L*, b*, and C* values.