Image reading apparatus

An image reading apparatus comprising:

• a guide plate that is movable between a first position and a second position and is configured to guide a medium at a first side thereof when disposed at the first position;
• a retention member that is rotatable about an axis intersecting a direction in which the medium is guided, that has a first side surface and a second side surface which has a curvature greater than a curvature of the first side surface, and that retains a plurality of color samples on the second side surface;
• a reading unit configured to read, at a reading position, an image formed on the medium guided by the guide plate;
• and
• a rotating unit configured to cause the retention member to rotate such that a second side of the guide plate and the first side surface face each other when the guide plate is disposed at the first position and the plurality of color samples are moved to the reading position when the guide plate is disposed at the second position.