main.css

.p-TabBar[data-orientation='horizontal'].theia-app-bottom {
    background: var(--theia-layout-color1);
}

.theia-output {
    background: var(--theia-arduino-terminal);
}

#outputView {
    color: var(--theia-ui-font-color3);
}

#arduino-verify.arduino-tool-icon {
    background: url(../icons/buttons.svg);
    background-size: 800%;
    background-position-x: 141px;
    background-position-y: 21px;
}

#arduino-upload.arduino-tool-icon {
    background: url(../icons/buttons.svg);
    background-size: 800%;
    background-position-x: 117px;
    background-position-y: 21px;
}

#arduino-verify.arduino-tool-icon:hover {
    background-position-y: 45px;
}

#arduino-upload.arduino-tool-icon:hover {
    background-position-y: 45px;
}

.p-TabBar-toolbar .item.arduino-tool-item {
    margin-left: 3px;
}

.arduino-tool-item.item.connected-boards {
    opacity: 1;
}

.arduino-tool-item.item.connected-boards  select {
    background: var(--theia-layout-color0);
}