Almost all the petal tips of the Lithops olivacea bud in picture are still caught in the "noose of sepals". The visible yellow here will eventually be on the outside, the lower side of the petals when the open flower faces the sun. This event can be expected soon, given the signs in proceedings.
The flowers are open by day and closed at night; Lithops is not a night pollination seeking genus.
The round-tipped sepals in picture are dull brown-red at their tips, and greener than the leaves at their bases.
The leaves are greyish on the sides, dark grey green and translucent on top, apart from some small, opaque islands scattered randomly. Fused at the base and closely adjusted in pairs at the top, these are clearly leaf bodies, not blades (Frandsen, 2017; Van Jaarsveld, et al, 2006; Smith, et al, 1998; iNaturalist; https://llifle.com; https://pza.sanbi.org).