Button turns blue on press (not outline, not select highlight)

As I could infer from your problem statement, the background-color of your button might be changing due to :active pseudo-class acting on it which stays for few seconds of click on button and then when click is released it disappears. You may target the button:active selector and override the behavior with the desired background-color and color. I have tried creating a mock of what may help you.

button{
background-color: blue;
color: #ffffff;
height: 32px;
}
/* scenario you might need to override with the background color you want to retain */
button:active{
background: darkblue;
}

<button type="submit">Trial</button>