For adding the material-fullpalette.min.css, you need to do make change in the following file
Location: bower_components\bootstrap-material-design\bower.json
For adding only material-fullpalette.min.css, just do following change
"main": [
"dist/css/material.css",
"dist/js/material.js",
"dist/css/ripples.css",
"dist/js/ripples.js",
"dist/css/material-fullpalette.css"
],
For adding other files, you need to do following
"main": [
"dist/css/material.css",
"dist/js/material.js",
"dist/css/ripples.css",
"dist/js/ripples.js",
"dist/css/material-fullpalette.css",
"dist/css/roboto.css",
"dist/fonts/Material-Design-Icons.eot",
"dist/fonts/Material-Design-Icons.svg",
"dist/fonts/Material-Design-Icons.ttf",
"dist/fonts/Material-Design-Icons.woff",
"dist/fonts/RobotoDraftBold.woff",
"dist/fonts/RobotoDraftBold.woff2",
"dist/fonts/RobotoDraftItalic.woff",
"dist/fonts/RobotoDraftItalic.woff2",
"dist/fonts/RobotoDraftRegular.woff",
"dist/fonts/RobotoDraftRegular.woff2"
],
Then if you run grunt, it will be automatically included in the main package.