The plant in question is also deficient in anthocyanins. These are a family of pigments within an umberella category of flavonoids, which give flowers pink, blue and purple colours. From a base molecule, anthocyanidin, the addition of various sugar molecules produces the 400+ known anthocyanins. Anthocyanidin requires five different enzymes working in concert. Different anthocyanins give flowers different hues at a given pH. In flowers they are probably responsible for attracting insect pollinators. In plants as a whole they have an anti-oxidant role (one that is lost after ingestion by mammals),

The theories of a genetic basis to lack of chlorophyll can be applied to anthocyanin production, with the proviso that it has to be a defect in the synthesis as far as anthocyanidin - the base substrate of the anthocyanins. The exception to this is that a heterozygote may produce less anthocyanins. Does this confer a disadvantage to the heterozygote for a genetic defect? It is estimated that 109 tons of anthocyanins are produced in nature per year. This outlines their importance to plants. Against this 2% of all hydrocarbons fixed in photosynthesis are converted into flavonoids. This is a large amount when you consider how much hydrocarbon compounds are required by each plant. The overheads on flavonoid production are heavy and the advantages they confer are just within the black. A heterozygote for a genetic defect would be compromised, but not too much. Looking at a normal population of E. helleborine one sees a range of depth of the pinks and purples. This will be the result of the presence and absence of different iso-enzyme genes for the different anthocyanins. Clearly a balance between the advantages of anthocyanins and the overheads of production has been reached. That said, a homozygote for an enzyme deficiency of one of the pre-anthocynidin products would possibly be at a disadvantage for insect pollination - just. E. helleborine var chlorantha does not occur in all colonies or populations, yet is widespread across the U.K. This fits with out-crossing of the parent populations combined with a small disadvantage of absence of anthocyanins. The same genetic faults would apply to the enzymes used for anthocyanin production as for chlorophyll production.

Of course, I am making the assumption that both plants in question have the same genetic defect preventing anthocyanin production. If the two plants have different underlying causes then what we see is entirely coincidental!