Added a "version" check for the flowers dependency:

If the flowers mod defines "flowers:flower_geranium" (as is the case with my update of 2012-08-01), then those will
be used to get blue pigment powder, and violas will produce violet powder, both of which can be directly used to
create their respective liquid dye colors.  If it is not defined (e.g. the user has an older version of the flowers
mod), then violas produce blue dye powder.  Violet dye can still be formed by mixing blue and magenta or blue and
red dyes, as before.

changelog.txt

@@ -1,6 +1,15 @@
 Changelog
 ---------
 
+2012-07-26: Added a "version" check for the flowers dependency:  If the
+flowers mod defines "flowers:flower_geranium" (as is the case with my update
+of 2012-08-01), then those will be used to get blue pigment powder, and violas
+will produce violet powder, both of which can be directly used to create their
+respective liquid dye colors.  If it is not defined (e.g. the user has an 
+older version of the flowers mod), then violas produce blue dye powder.  Violet
+dye can still be formed by mixing blue and magenta or blue and red dyes, as
+before.
+
 2012-07-26: Better bottle textures.  Note that these are blended against the 
 50% grey field they normally appear on in the inventory display, so they will 
 show artifacts if you try to wield them.  Don't do that. :-)

init.lua

@@ -61,16 +61,14 @@ pigments = {
 	"red",
 	"orange",
 	"yellow",
-	"green",
-	"blue",
+	"green"
 }
 
 dyesdesc = {
 	"Red",
 	"Orange",
 	"Yellow",
-	"Green",
-	"Blue",
+	"Green"
 }
 	
 colorsources = {
@@ -78,10 +76,9 @@ colorsources = {
 	"flowers:flower_tulip",
 	"flowers:flower_dandelion_yellow",
 	"flowers:flower_waterlily",
-	"flowers:flower_viola",
 }
 
-for color = 1, 5 do
+for color in ipairs(colorsources) do
 
 	groupcolor = 
 	-- the recipes to turn sources into pigments
@@ -333,7 +330,45 @@ minetest.register_craft( {
 		},
 })
 
--- Violet
+-- Red-violet
+
+minetest.register_craftitem("unifieddyes:redviolet", {
+        description = "Full Red-violet Dye",
+        inventory_image = "unifieddyes_redviolet.png",
+	groups = { dye=1, excolor_red_violet=1, unicolor_red_violet=1 }
+})
+
+minetest.register_craft( {
+       type = "shapeless",
+       output = "unifieddyes:redviolet 2",
+       recipe = {
+               "unifieddyes:red",
+               "unifieddyes:magenta",
+		},
+})
+
+-- We need to check if the version of the Flowers mod that is installed
+-- contains geraniums or not.  If it doesn't, use the Viola to make blue dye.
+-- If Geraniums do exist, use them to make blue dye instead, and use Violas
+-- to get violet dye.  Violet can always be made by mixing blue with magenta
+-- or red as usual.
+
+
+minetest.register_craftitem("unifieddyes:pigment_blue", {
+	description = "Blue Pigment",
+	inventory_image = "unifieddyes_pigment_blue.png",
+})
+
+minetest.register_craftitem("unifieddyes:blue", {
+	description = "Full Blue Dye",
+	inventory_image = "unifieddyes_blue.png",
+	groups = { dye=1, basecolor_violet=1, excolor_violet=1, unicolor_violet=1 }
+})
+
+minetest.register_craftitem("unifieddyes:pigment_violet", {
+        description = "Violet Pigment",
+        inventory_image = "unifieddyes_pigment_violet.png",
+})
 
 minetest.register_craftitem("unifieddyes:violet", {
         description = "Full Violet/Purple Dye",
@@ -360,22 +395,26 @@ minetest.register_craft( {
 		},
 })
 
--- Red-violet
+if minetest.registered_nodes["flowers:flower_geranium"] == nil then
 
-minetest.register_craftitem("unifieddyes:redviolet", {
-        description = "Full Red-violet Dye",
-        inventory_image = "unifieddyes_redviolet.png",
-	groups = { dye=1, excolor_red_violet=1, unicolor_red_violet=1 }
-})
+	minetest.register_craft({
+		type = "cooking",
+		output = "unifieddyes:pigment_blue 2",
+		recipe = "flowers:flower_viola",
+	})
+else
+	minetest.register_craft({
+		type = "cooking",
+		output = "unifieddyes:pigment_blue 2",
+		recipe = "flowers:flower_geranium",
+	})
 
-minetest.register_craft( {
-       type = "shapeless",
-       output = "unifieddyes:redviolet 2",
-       recipe = {
-               "unifieddyes:red",
-               "unifieddyes:magenta",
-		},
-})
+	minetest.register_craft({
+		type = "cooking",
+		output = "unifieddyes:pigment_violet 2",
+		recipe = "flowers:flower_viola",
+	})
+end
 
 
 -- =================================================================