The original description of Rebutia (Aylostera) mixticolor was published in Kakteen und andere Sukkulenten 28(4): 76, 1977, the journal of the Deutsche Kakteen-Gesellschaft, by Friedrich Ritter.

Here is the text in Latin as published, with my own English translation below. You should look up the original description for more details.

Rebutia mixticolor Ritter spec. nov.

Solitaria, in apricatione vilocea, 2-4 cm crassa, humilis, radice rapacea; costae 11-13, 3-5 mm altae, valde crenatae; areolae 2 mm longae, subnudae, 5-8 mm inter se remotae; spinae solum marginales, lateraliter directae, brunneae, postea albae, 3-7 mm longae, 6-11.

Flores 3-4 cm longi ; ovarium lana alba et plerumque saetis albidis instructum; stylus 1—5 mm cum tubo coalitus, sulcus nectarifer 1-3 mm longus; tubus floralis 6-13 mm longus; filamenta rosacea; stylus viridis, stigmata 6-8 flavoviridia vel flava; petala 14-20 mm longa, 5-9 mm lata, spathulata, coloribus mixtis purpureo et igneo; semina atrobrunnea, 1,5 mm longa, vix tuberculata.

Habitat San Antonio, Prov. Mendez, Bolivia.

Collected as FR1108.

English translation

Rebutia mixticolor Ritter spec. nov.

Single, violaceous in appearance, 2 – 4cm thick, low, with a tap root; 11 – 13 ribs, 3 – 5mm high, very notched; areoles 2mm long, almost bare, with 5 – 8mm between each; marginal spines only, 6 – 11, pointing laterally, brown, later white, 3 – 7mm long.

Flowers 3 – 4cm long; ovary with white wool and generally with whitish bristles; style fused with tube for 1 – 5mm, nectary groove 1 – 3mm long; floral tube 6 – 13mm long; stamens pinkish; style green with 6 – 8 yellowish-green to yellow stigmas; petals 14 – 20mm long, 5 – 9mm wide, spatulate, colour mixed purple and fiery red; seeds dark brown, 1.5mm long, slightly warty.

Habitat San Antonio, Prov. Mendez, Bolivia.

Collected as FR1108.