I re-bolded the sections your looking for. These are brush links. Brushes tell the game which texture sheet to look at, where on the sheet and how big is the icon. The easiest way for you would be to replace the brush names with the brush names of the star you are using. If you are replacing this with white star then open the white star entity and use those brush links.
example for 1 brush link. I'm guessing here.
farIcon "HUDICON_SOLARSYSTEM_GREEN"
farIcon "HUDICON_SOLARSYSTEM_WHITE"
TXT
entityType "Star"
coronaStartColor ff94c012
coronaEndColor ff217001
coronaStartColorDistance 0.000000
coronaEndColorDistance 1.000000
farIcon "HUDICON_SOLARSYSTEM_GREEN"
coloredSkyboxMeshNameCount 4
meshName "SkyboxBackdrop2"
meshName "SkyboxBackdrop3"
meshName "SkyboxBackdrop4"
meshName "SkyboxBackdrop6"
deepSpaceSkyboxMeshNameCount 1
meshName "SkyboxBackdrop7"
iconTextureName "starcore-green"
ability:0 "AbilitySolarRegeneration"
ability:1 ""
ability:2 ""
ability:3 ""
hudIcon "HUDICON_STAR_GREEN"
smallHudIcon "HUDICONSMALL_STAR_GREEN"
infoCardIcon "INFOCARDICON_STAR_GREEN"
minZoomDistanceMult 2.000000
moveAreaRadius 60000.000000
hyperspaceExitRadius 50000.000000
isWormhole FALSE
mainViewIcon "MAINVIEWICON_STAR_GREEN"
picture "STARPICTURE_GREEN"
MeshName "Star_Green"
MaxMeshVisibilityDistanceToCamera -1.000000
minShadow 0.000000
maxShadow 0.000000
I would have just remove the GreenStar from the GalaxyScenarioDef.galaxyScenarioDef and entity.manifest and updated all the counts.