You're welcome kimpeito.
Lin, what I found is confusing. There is another plant, which is similar to yours and which is similar to Euphorbia grantii, it doesn't appear to have the leaf scars on the stems and as you say it changes colour according to sun or not.
On the Plant List, Synadenium grantii Hook.f. is a synonym of Euphorbia umbellata (Pax) Bruyns
http://www.theplantlist.org/tp...
I checked on the Catalogue of life,Synadenium grantii Hook.f. is a synonym of Euphorbia umbellata (Pax) ined.
http://www.catalogueoflife.org...
Euphorbia grantii Oliv. is accepted on the CoL. where Synadenium grantii Hook.f. is a synonym.
http://www.catalogueoflife.org...
Euphorbia grantii Oliv. is accepted on the CoL. (another entry but no mention of synonym Synadenium grantii Hook.f)
http://www.catalogueoflife.org...
Euphorbia grantii Oliv. is also accepted on The Plant List.
http://www.theplantlist.org/tp...
Euphorbia grantii - Synadenium grantii comes up in a search for Euphorbia grantii ..
https://www.google.co.uk/searc...
Euphorbia umbellata on google comes up with a plant which looks like yours .. and it's being given Synadenium grantii as a synonym! The leaves vary between green and red with splashes of red. That looks to be consistent, where a search for Euphorbia grantii generally comes up with the plant with leaf scars and either red or green leaves some of which are named Synadenium grantii f. rubrum. I would say the "f. rubrum" is the scientific name as a "rubrum" form of the species, with "Rubrum" being a name given for the purposes of selling at nurseries as often is the case (people like given names).
https://www.google.co.uk/searc...
There could be some mixing up and confusion between these plants but the "Rubrum" form is in the plant files.
