:root
{
--blue: #007AB5;
--indigo: #3B55C4;
--cyan: #00C0E8;
--light-blue: #8FDAFF;
  --lighter-blue:#ADE8FF;
}

body
{
  background: var(--blue);
}

header, section, div
{
  border:double 6px; padding:20px; margin:6px;
}

header, .subcolor, .button
{
  background:white;
  text-align:center;
}
section
{
  background: var(--lighter-blue);
}

#blue{color:var(--blue)}
#indigo{color:var(--indigo)}
#cyan{color:var(--cyan)}

#problem1
{
color: white;
background:blue;
border:double 6px black; padding:10px;
}
#problem2
{
color: black;
background:#7878FF;
border:double 6px black; padding:10px;
}