Diamond nanoparticles are mainly produced along two methods : (i) by detonation synthesis (DND), giving rise to quasi-monodisperse but defective 5 nm particles or (ii) by milling of synthetic or natural diamond (MND), which preserves the crystalline quality with unique semiconducting assets of bulk diamond for energy-related applications. Such MND are also suitable to host NV or SiV color centers currently intensively studied for nanomedecine and quantum applications. For such applications, a fine control of their colloidal properties is required, especially when their surface is hydrogenated. If the route towards stable suspensions of hydrogenated DND in water is well identified, nowadays, providing colloidal stability on long period of time to hydrogenated MND is still a challenge. The present study aims to investigate the colloidal stability in water of 50 nm hydrogenated MND obtained by thermal hydrogenation using pressures ranging from 10 mbar up to atmospheric pressure. We will show that we successfully obtain stable suspensions of hydrogenated MND over months. Colloidal properties of the different H-MND (monitored by DLS, zetametry and SAXS) will then be correlated to an extended characterization of their surface chemistry and morphology via a combination of FTIR, XPS, Raman, SEM and XRD investigations. The influence of the hydrogen coverage and the residual sp2 carbon on ND colloidal stability will also be investigated. Finally, the behavior of hydrogenated DND and MND will be compared and the origin of their respective stability will be discussed