Identifying blocks of data in excel data input

I need to read data from large excel files that are composed of smaller blocks that are typically separated by free spaces and have different numbers of rows (but for now, the same nubers of columns).

The data is composed both of numbers and strings, so I usually read the whole set in raw format using:

[NUMM,STRR,RAWW]=xlsread(InFile,1)

Then I perform the required operations on them. However, I need to separate the data into smaller blocks (and subsequently, separate arrays) as shown in figure and treat each block differently, so that I will have arrays by names YellowMatrix, RedMatrix, OrangeMatrix, BlueMatrix etc. How can I do this without using a loop?