Reka - Without seeing the file, some things to try:

Table View: View Toolbar: Colour > Row variation > Strong (right click to return to default)

The numeric and date graded colour range columns display may be affected in the Table View by extreme values. Experiment with changing the way the start, middle and end colours are mapped and the way the range is calculated.

Main Toolbar: Settings > Colour ranges > change range colours and mapping algorithm

Also, try changing the global colour pallette:

Main Toolbar: Style > Data colours > change settimngs for category and continuous colours