Okay, first you need to open your save file with a text editor. Save files are here:
Win: C:\Users\*username*\AppData\LocalLow\Glitch Pitch\Idol Manager\data
Mac: ~/Library/Application Support/Glitch Pitch/Idol Manager/data/
Find your idol in data_girls__Girls and find her "textureAssets". You can change her appearance by editing "asset_id" parameters. You can get IDs from this folder: *game_folder*\IM_Data\StreamingAssets\Textures\IdolPortraits
"textureAssets": [
{
"type": 0, <- Body
"asset_id": "0 5 0"
},
{
"type": 1, <- Hair
"asset_id": "1 5 1" <- First number = same as "type". Second number = Body ID. Third number = Asset ID.
},
{
"type": 2, <- Face
"asset_id": "2 5 1"
},
{
"type": 3, <- Accessory
"asset_id": "3 5 0"
}
],