You can often see a rainbow in a spray of water such as from sprinkler irrigation. Is the brocha for a rainbow applicable in that case?
Also, does a rainbow that comes from a prism get a brocha too?
In a book I own called שער העין - Shaar HaAyin by a Rabbi Eliyahu Ariel in Chapter 7 Footnote 14 he says that this does not qualify for the special blessing on a rainbow as that was only for rainbows in clouds which are similar to the one by Noah. However, he suggests that it qualifies as an amazing natural wonder (similar to lightning) and would therefore deserve a Oseh Maaseh Vereishit like lightning. He concludes that as it is a matter of doubt, one should recite the blessing of Oseh Maaseh Vereishit but omit God's name from the blessing.
EDIT: In the book he is talking about a rainbow you can see sometimes near a waterfall. As the prism and sprinkler are artificial (and certainly not Maaseh Vereishit) it is likely that even he would agree not to say any blessing at all upon these rainbows.