I want to export my objects to unity, but in blender I`m using Eevee engine. However the light in rendered more and material preview mode is completely different, which impacts the colors of objects. Which one can i trust to see the true final colors of the objects so that they will be the same when i export them to unity?
Material Preview uses one of the builtin generic HDRi maps to light the objects.
It is for preview purposes only and wont affect final scene lighting, nor will it be exported along with the model.
In this mode scene lights are ignored (optionally) for performance and workflow reasons. You can enable them in the Shading Popover.
Render preview uses your actual World Shader as background color instead and lighting.
Scene lights are also previewed closer to final result. They are still never exported to other applications though, so in external game engine or environments results will always differ.
You can switch the HDRi on/off for both preview modes.
Also see related How to use Default HDRIs in Renders?