/*  phpBB3 Style Sheet
    --------------------------------------------------------------
	Style name:			prosilver (the default phpBB 3.2.x style)
	Based on style:
	Original author:	Tom Beddard ( http://www.subblue.com/ )
	Modified by:		phpBB Limited ( https://www.phpbb.com/ )
    --------------------------------------------------------------
*/

@import url("normalize.css?v=3.2");
@import url("base.css?v=3.2");
@import url("utilities.css?v=3.2");
@import url("common.css?v=3.2");
@import url("links.css?v=3.2");
@import url("content.css?v=3.2");
@import url("buttons.css?v=3.2");
@import url("cp.css?v=3.2");
@import url("forms.css?v=3.2");
@import url("icons.css?v=3.2");
@import url("colours.css?v=3.2");
@import url("responsive.css?v=3.2");
/* =======================================================
   Attachment Row & Inline Display — Final Clean Version
   ======================================================= */

/* Row background */
#file-list .attach-row,
#file-list li {
    background-color: #1e1e1e !important;
    border-bottom: 1px solid #333333 !important;
}

/* Filename text only */
#file-list .attach-row .file-name {
    color: #ffd700 !important;
    font-weight: bold !important;
    background: transparent !important;
}

/* File size text only */
#file-list .attach-row .file-size {
    color: #cccccc !important;
    background: transparent !important;
}

/* Comment textbox only (NOT buttons) */
#file-list .attach-row textarea,
#file-list .attach-row input[type="text"] {
    background-color: #333333 !important;
    color: #ffffff !important;
    border: 1px solid #555555 !important;
}

/* Side-by-side inline attachments in posts */
.postbody .content dl.file,
.postbody .content dl.thumbnail,
.attachbox dl.file,
.attachbox dl.thumbnail {
    display: inline-block !important;
    vertical-align: top !important;
    margin: 6px 14px 6px 0 !important;
    clear: none !important;
}

.postbody .content dl.file dt.attach-image,
.postbody .content dl.thumbnail dt,
.attachbox dl.file dt.attach-image,
.attachbox dl.thumbnail dt {
    display: block !important;
    text-align: center !important;
}

.postbody .content dl.file dd,
.postbody .content dl.thumbnail dd,
.attachbox dl.file dd,
.attachbox dl.thumbnail dd {
    margin: 3px 0 0 0 !important;
    text-align: center !important;
    max-width: 260px !important;
    word-break: break-word !important;
}
/* Kill phpBB zebra striping on the attachment table + force dark cells */
table.zebra-list tbody#file-list tr td,
table.zebra-list tbody#file-list tr:nth-child(even) td,
table.zebra-list tbody#file-list tr:nth-child(odd) td,
#file-list tr.attach-row td {
    background-color: #1e1e1e !important;
    border-top-color: #333333 !important;
}

/* Kill phpBB zebra striping on the attachment table + force dark cells */
table.zebra-list tbody#file-list tr td,
table.zebra-list tbody#file-list tr:nth-child(even) td,
table.zebra-list tbody#file-list tr:nth-child(odd) td,
#file-list tr.attach-row td {
    background-color: #1e1e1e !important;
    border-top-color: #333333 !important;
}

/* Filename text */
#file-list td.attach-name,
#file-list td.attach-name a {
    color: #ffd700 !important;
    font-weight: bold !important;
}

/* File size / comment / status cells */
#file-list td.attach-filesize,
#file-list td.attach-comment,
#file-list td.attach-status {
    color: #cccccc !important;
}
/* Force attachment boxes to sit side-by-side */
dl.attachbox {
    float: left !important;
    clear: none !important;
    max-width: 260px !important;
    width: auto !important;
    margin: 5px 10px 10px 0 !important;
}

/* Make sure the ATTACHMENTS container doesn't collapse/clear its floats oddly */
.postbody .attachbox-list,
#page-body .attachbox-list {
    overflow: visible !important;
}

/* Clearfix so content after attachments doesn't overlap them */
.postbody .content::after {
    content: "";
    display: table;
    clear: both;
}
/* Each attachment <dd> becomes an inline-block "card" */
dl.attachbox > dd {
    display: inline-block !important;
    vertical-align: top !important;
    margin: 0 15px 15px 0 !important;
}

/* Keep the thumbnail itself well-behaved inside its card */
dl.attachbox dl.thumbnail {
    display: inline-block !important;
    max-width: 260px !important;
}

dl.attachbox dl.thumbnail img {
    max-width: 100% !important;
    height: auto !important;
}
#page-body dl.attachbox > dd,
.postbody dl.attachbox > dd,
div.content + dl.attachbox > dd {
    display: inline-block !important;
    vertical-align: top !important;
    margin: 0 15px 15px 0 !important;
}
dl.attachbox {
    display: block !important;
    float: none !important;
    width: 100% !important;
    max-width: 100% !important;
    clear: both !important;
}
.phpbb_alert {

    color: #000 !important;

}

Or if the theme uses a custom class:

css

#darkenwrapper .alert_text {

    color: #000 !important;

}