The phrase "colder object" refers to an object that has less heat or lower temperature compared to another object. It is used to describe two things relative to each other, where one is colder than the other. Full definition
Do you still think that colder objects do not emit IR radiation? (wattsupwiththat.com)
Most of the snapshots turn out to be duds, but on March 15 he announced that one series of them had captured something extraordinary: the farthest, coldest object in the solar system and the largest new member of the sun's family of planetlike objects since the discovery of Pluto in 1930. (discovermagazine.com)
This sensory confusion, which neurologists call the thermal - grill illusion, may occur because cold objects touching the skin simultaneously stimulate both fast - conducting (A-delta type) nerve fibers that signal cold and slower (C type) fibers that signal pain. (discovermagazine.com)