For this, you simply have to pass the specific property of a tool in your Unlayer Initiation code. Please follow our documentation, where each property is described in detail.
For example, if you want to change default color of button tool you have to use this:
unlayer.init({
tools: {
button: {
properties: {
buttonColors: {
value: {
color: "#FFFFFF",
backgroundColor: "#3AAEE0",
hoverColor: "#FFFFFF",
hoverBackgroundColor: "#3AAEE0"
}
}
}
}
}
});