finding region in image and change color

[ashwini]

hello.. thanks for viewing

case 1> i am trying to find out the region in an image .i refer t-shirt eg. done by masking i applied on following image:
this is earth.png

1. convert earth.png -modulate 100,100,33.3 -colorspace HSL -channel Hue,Saturation -separate +channel ( -clone 1 -background none -fuzz 30% -transparent black ) -delete 1 -alpha extract -compose multiply -composite mask1.png

got output as foll. mask1.png

then i done next step

2.convert mask1.png -negate mask2.png


3convert earth.png -mask mask2.png -modulate 100,100,66.6 cearth.png


can u help me to figure out what first command actually does ? as in girl in pink t shirt eg. ( -clone 0 -background none -fuzz 5% -transparent gray64 ) used because gray background present..as per my understanding . so i removed that line while applying to earth image then it gave mask i.e mask1.png
and got final image but it changing original img blue color which was not happen in t-shirt eg.
********************************************************************************************************************************************************************
case 2>

also if i want change suppose #304878 color region i.e blue color in earth image then i gave

convert earth.png -fuzz 25% -fill none +opaque #304878 maske1.png


convert maske1.png -negate write_mask.png
then

convert earth.png -mask write_mask.png -modulate 100,100,133.3 +mask cearth_yellow.png


i am expecting i this 2nd case the output should be blue region from earth.png turns into yellow as 133.3, but it turn to violet please help me to understand this..

thanks