styles.css

:root {
    --rowNumber: 16;
    --columnNumber: 16;
}

body {
    background-color: lightgoldenrodyellow;
}

#container {
    display: flex;
    flex-direction: column;
    align-items: center;
}

#panel {
    display: flex;
    flex-direction: column;
    margin-top: 2rem;
}

#buttons {
    display: flex;
    flex-direction: row;
    justify-content: space-between;
    margin-bottom: 1rem;
}

#mainBlock {
    display: grid;
    grid-template-columns: repeat(var(--columnNumber), 1fr);
    grid-template-rows: repeat(var(--rowNumber), 1fr);
    width: 512px;
    height: 512px;
    background-color: white;
    margin-top: 1rem;
    border: 1px black solid;
}

.singleCell {
    display: block;
    border: solid 1px rgb(238, 238, 238);
}

.btn {
    height: auto;
    padding: 4px;
}

#rgbColor, #greyColor {
    display: inline-block;
    vertical-align: middle;
    margin-left: 8px;
    width: auto;
    height: 22px;
    border-radius: 4px;
}

#singleColor, #rgbColor, #greyColor {
    width: 34px;
    height: 18px;
    border: 1px solid black;
    border-radius: 4px;
}

#singleColor:hover, #rgbColor:hover, #greyColor:hover {
    background-color: white;
    box-shadow: 4px 4px 3px rgba(28, 32, 32, 0.5);
    
}

#insideColor, #insideGrey {
    width: 24px;
    height: 7px;
    margin: 4px auto;
    border: 1px solid black;
}

#insideColor {
    background-image: linear-gradient(to right, red,orange,yellow,green,blue,indigo,violet);
}

#insideGrey {
    background-image: linear-gradient(to right, lightgrey, rgb(68, 66, 66));
}

#clr {
    margin-right: 8px;
}

#profile {
    width: 32px;
    height: auto;
    margin: 0 1rem;
}

#mark {
    margin-left: 1rem;
}

#copyright {
    margin-top: 6rem;
}