Anagallis arvensis var. arvensis

red pimpernel, red chickweed, poorman's barometer, shepherd's weather glass, or shepherd's clock, Blue Pimpernel • Hindi: नील Neel, Dharti Dhak, Krishnaneel • Marathi: रान द्राक्ष Ran draksh • Malayalam: Bellichina • Kannada: Suryakanti soppu;  

The confusion of Pimpernels: Let us be on look out: The common pimpernel has confused both field workers and reputed authors alike, but luckily the confusion seems to have been resolved more recently. Carolus Linnaeus, the Father of Taxonomy described two closely related species of Anagallis:
Anagallis arvensis L., the scarlet pimpernel with orange-scarlet to scarlet flowers
Anagallis caerulea L., the blue pimpernel with blue flowers
The two are now treated as two varieties var. arvensis and var. caerulea (L.) Gouan of Anagallis arvensis L.
Schreber, Spic. Fl. Lips. 5 1771 described a related species Anagallis coerulea (note slight difference in spellings), also used by Lamarck, a taxon that had been long treated as same var. caerulea of A. arvensis. It was only in 1972 that Fergussen established it to be a synonym of a distinct species Anagallis foemina Miller (1768). The plant List treats this as Anagallis arvensis subsp. foemina (Mill.) Schinz & Thell. Important to note that this taxon always has blue flowers.
This is how the two species can be differentiated:
Anagallis arvensis                                                                    Anagallis foemina
(or Anagallis arvensis subsp. arvensis)                             (or Anagallis arvensis subsp. foemina (Mill.) Schinz & Thell.)
1. Flowers scarlet (var. arvensis) or blue (var. caerulea)        1. Flowers blue
2. Pedicel in flower longer than subtending leaf.                     2. Pedicel in flower shorter or equal to the subtending leaf.
3. Sepals shorter than petals especially in bud                       3. Sepals equalling or longer than petals especially in bud
4. Petal margins overlapping                                                   4. Petal margins not overlapping
5. Petal margins with numerous hairs tipped with                   5. With few or no hairs, which if present have elongate
    globose glands.                                                                             terminal cells.

Let us look for our blue pimpernel (blue flowered Anagallis) more closely in light of above information to find its exact identity. Who knows we may have both taxa in India.
Anagallis arvensis L. subsp. arvensis
Photographed from Sunnyvale, California. 
Again very beautiful...
2 posts by 2 authors. Attachments (3).
Anagallis arvensis L. var. arvensis
scarlet pimpernel
This plant is commonly found in temperate climate and has orange to scarlet flowers.
Photographed from Srinagar, Kashmir

Attached are pictures of Anagallis arvensis ssp arvensis from San Francisco, USA captured in May 2013.
Requested to please validate the ID.
Yes ... Very good photographs
Flora-Australia-23: 1 correct image as above.
Anagallis arvensis -blue and scarlet plants growing in tufts on weedy areas.
Ana-( Greek-) is again and- agallein means to delight in. flowers indeed are delightful.

Really good pictures....have never seen scarlet ones..