Refer to figure.
The speeds referred to in the question are different operational speed limits applicable to aircraft certified under CS-23 and CS-25. These speed limits are based upon design speed limits defined during the certification process. The relevant design speed limits are:

V_C - The design cruising speed - the maximum cruising speed. The aircraft is certified to fly at this speed even at the limits of the acceleration range for the particular aircraft category, positive and negative. Above V_C, the aircraft structure may be damaged even if operating within the certified acceleration range (e.g. -1.0 g to 2.5 g for CS-25).

V_D - The design dive speed - this is the maximum speed for which the aircraft is certified. Flight above this speed may lead to structural failure, and flutter of aircraft surfaces may be experienced. V_C must not be more than 80% of V_D. The aircraft may not be certified to fly within the entire acceleration envelope at V_D (for CAT aircraft certified under CS-25, V_D is only tested from 0 g to 2.5 g).

Operational speed limits are then defined for CS-23 or CS-25 aircraft as follows:

CS-23

V_NO - The maximum structural cruise speed - This speed must not be greater than V_C. It is shown to the pilot on the ASI as the beginning of the yellow arc, where the green arc ends. It must also be less than 89% of V_NE

V_NE - The "never exceed" speed - Equal to 90% of V_D, to allow a safety margin below the maximum speed for which the airframe has actually been tested at (V_D). This margin is small however, so the pilot must never exceed V_NE, hence its apt name. On an ASI, V_NE is denoted by a red line at the end of the yellow speed range.

CS-25

V_MO- The maximum operating speed - Must not be greater than V_C. Unlike V_NO, this speed must not be intentionally exceeded at any stage throughout the flight. Expressed as an EAS.

M_MO- The maximum operating Mach number - At high altitude as Mach number increases, M_MO becomes the limiting speed, expressed as a Mach number. Above this speed, high speed buffeting may be experienced.

So the relevant speed limits for transport category aircraft are V_MO and M_MO.