表情符号在我的AngularDart项目中不呈现颜色

在angular dart项目中,我试图用应用程序名和表情符号填充欢迎页面,但结果并没有呈现颜色。它只以黑色填充。请帮忙。

<div class="yns-welcome">
    <div class="yns-app-icon">{{appIcon}}</div>
    <div class="yns-main-header">{{appTitle}}</div>
    <div class="yns-sub-header">{{appSubtitle}}</div>
    <div class="yns-main-footer">{{appMainFooter}}</div>
    <div class="yns-sub-footer">{{appSubFooter}}</div>
</div>

app_组件。css

:host {
    font-family: "Lucida Sans Unicode", "Lucida Grande", sans-serif;
}

.yns-welcome {
    height: 100%;
    justify-content: center;
    align-items: center;
    display: flex;
    flex-direction: column;
    text-align: center;
}

.yns-app-icon {
   font-size: 125px;
}

.yns-main-header {
    font-size: 40px;
}

.yns-sub-header {
    padding: 0 0 20px;
    font-size: 16px;
}

.yns-login-btn {
    background-color: dodgerblue;
    margin: 20px 0;
}

.yns-main-footer {
    font-size: 12px;
    padding: 5px 0 10px;
}

.yns-sub-footer {
    font-size: 10px;
}