How to change App Drawer background to be less transparent

the app drawer background color can be changed by editing "user-shell" theme's .css file.

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Please note that, with this answer, the background is not fully covered with the color we want, still edges, and the second page are transparent.

Take Backup of "user-shell" theme's .css file you are using.

If you are not using custom user-shell theme, below are the default files.

for Ubuntu 18.04 /usr/share/gnome-shell/theme/ubuntu.css
for Ubuntu 19.04 & 19.10 /usr/share/gnome-shell/theme/Yaru/gnome-shell.css

Open the file, find the below content.

/* App Vault/Grid */
.icon-grid {
  spacing: 30px;
  -shell-grid-horizontal-item-size: 136px;
  -shell-grid-vertical-item-size: 136px; }
  .icon-grid .overview-icon {
    icon-size: 96px; }

and change it like below, replace any color you want in place of rgba field.

/* App Vault/Grid */
.icon-grid {
  spacing: 30px;
  -shell-grid-horizontal-item-size: 136px;
  -shell-grid-vertical-item-size: 136px;
  background-color: rgba(71, 68, 68, 1); }
  .icon-grid .overview-icon {
    icon-size: 96px; }

Observe i have edited line number 1321 and added this under line number 1321
background-color: rgba(71, 68, 68, 1); }

Save the file, Close & Reboot or Logout and Login to see the Change.

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